Enjoy your morning with a slice of Rhubarb Oatmeal Breakfast Cake! It’s got tangy rhubarb, hearty oats, and loads of cinnamon sugar in every bite. This is an incredible recipe perfect for the season.
Rhubarb and cinnamon pair so well together. I love how the addition of oatmeal adds a deeper texture too the cake too.
This cake is really easy to put together. It comes together in a few steps and is perfect for breakfast, a snack, or a post-dinner treat.
For more rhubarb recipes, try Rhubarb Cake, Rhubarb Muffins, and Rhubarb Cinnamon Roll Cake.
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Why this recipe is so good
- Breakfast idea – This is a great recipe to make ahead of time and then enjoy with your morning coffee!
- Rhubarb - A delicious use of rhubarb during the season.
- Easy to make – This cake comes together with just a few simple steps!
Ingredients Notes
Full recipe and ingredients are in the recipe card below. Feel free to scroll through this section to view certain key ingredients we’re using!
- Butter – This will be softened. I always use unsalted for baking.
- Buttermilk - You can also use full fat kefir or plain yogurt. To make buttermilk, stir 3/4 cups of milk with 1 1/2 tbsp of lemon juice. Allow to sit on your counter for at least 10 minutes before using.
- Cinnamon - An essential spice in this recipe.
- Cornstarch – This helps add a tender crumb to the cake.
- Eggs – Make sure they’re at room temperature before beginning.
- Flour – All-purpose flour is used in this recipe.
- Rhubarb - I used red rhubarb for that pop of colour in the cake. Regardless of the colour, it will still be tangy. Slice them into pieces (see photos below for reference). Rhubarb that is older in the season will be tougher and more stringy, so you may peel it if you want.
- Oats – Make sure you use rolled oats, also known as large flake oats. Quick oats will not work.
- Leavening agents - Both baking soda & baking powder are used in this recipe. Make sure they are not expired.
- White sugar - Also known as granulated sugar.
Step by step instructions
Here is how to make and bake this rhubarb oatmeal breakfast cake. You will need a 9×9 baking pan lined with parchment paper, 3 mixing bowls, a spatula, and an electric handheld mixer.
Step 1 – Prep. Grease the pan. For easy removal of the cake, place parchment paper on the bottom and 2 sides of the pan. Gently grease the other two sides and then set aside.
Step 2 – Mix dry ingredients. In a medium sized bowl, add in flour, oats, cinnamon, cornstarch, baking soda, baking powder, and salt. Stir to combine and set aside.
Step 3 – Cream the butter and sugar. In a large bowl, add softened butter and white sugar. Beat on medium speed for 2-3 minutes until it’s light and fluffy. Make sure to scrap the sides of the bowl.
Step 4 – Add in wet ingredients. Add in the eggs, buttermilk, and vanilla. Continue mixing on medium speed. It’s okay if it is clumpy.
Step 5 – Add in dry ingredients. Mix in the dry ingredients and using a spatula, gently fold until a batter forms. Do not over-mix!
Step 6 - Add in rhubarb. Add 2 tbsp of flour into the rhubarb and toss it around, evenly coating the rhubarb pieces in flour. This will help prevent them from sinking to the bottom. Then mix the rhubarb in a few times. Don't over-mix!
Step 7 – Bake. Spread the batter into the prepared pan evenly. Sprinkle extra white sugar on top. This will give you a sweet crunchy top.
Bake for 40-45 minutes. It really depends on your oven, but after 35 minutes I would start checking with a toothpick to see if it’s ready! A toothpick should come out clean.
Allow to cool, slice, and enjoy! This rhubarb oatmeal breakfast cake is soo good! It stays good on the counter for a day in an airtight container, and in the refrigerator for 5 days!
Expert Baking Tips
Here are a few expert baking tips from my kitchen to yours
- Use a gram scale. I cannot emphasize this enough! It is the most accurate way of measuring your ingredients in the kitchen. This is one of my favourites.
- Do not over-mix! A big reason cakes don’t rise or turn out tough is because the batter is over-mixed. Once you see no flour streaks, stop mixing.
- Toss the rhubarb in flour. This is important as rhubarb carries a lot of juices that come out during baking. The extra flour will help absorb any!
- To make ahead of time: Bake, cool, slice, and store in an airtight container or wrap in foil/saran wrap.
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Rhubarb Oatmeal Breakfast Cake
Ingredients
- 1/2 cup unsalted butter softened
- 3/4 cups white sugar + extra 2 tbsp for dusting
- 2 eggs room temperature
- 1 tbsp vanilla
- 3/4 cups buttermilk* room temperature
- 1 1/4 cups all-purpose flour + 2 tbsp for dusting
- 1 cup rolled oats
- 1 tbsp cornstarch
- 1/2 tsp baking soda
- 1 1/2 tsp baking powder
- 1/4 tsp salt
- 1/4 tsp cinnamon
- 2 cups fresh rhubarb sliced in thin slices
Instructions
- Preheat the oven to 350℉/180℃. For easy removal of the cake, place parchment paper on the bottom and 2 sides of the pan. Gently grease the other two sides and then set aside.
- In a medium sized bowl, add in the dry ingredients. Stir to combine and set aside.1 1/4 cups all-purpose flour, 1 cup rolled oats, 1 tbsp cornstarch, 1/2 tsp baking soda, 1 1/2 tsp baking powder, 1/4 tsp salt, 1/4 tsp cinnamon
- In a large bowl, add softened butter and white sugar. Beat on medium speed for 2-3 minutes until it’s light and fluffy. Make sure to scrap the sides of the bowl.1/2 cup unsalted butter, 3/4 cups white sugar
- Add in the eggs, buttermilk, and vanilla. Continue mixing on medium speed. It’s okay if it is clumpy.2 eggs, 1 tbsp vanilla, 3/4 cups buttermilk*
- Mix in the dry ingredients and using a spatula, gently fold until a batter forms. Do not over-mix!
- Add 2 tbsp of flour into the rhubarb and toss it around, evenly coating the rhubarb pieces in flour. This will help prevent them from sinking to the bottom. Then mix the rhubarb in a few times. Don't over-mix!2 cups fresh rhubarb
- Spread the batter into the prepared pan evenly. Sprinkle extra white sugar on top (approx 2 tbsp). This will give you a sweet crunchy top.
- Bake for 40-45 minutes. It really depends on your oven, but after 35 minutes I would start checking with a toothpick to see if it’s ready! A toothpick should come out clean.
- Allow to cool, slice, and enjoy! This rhubarb oatmeal breakfast cake is soo good! It stays good on the counter for a day in an airtight container, and in the refrigerator for 5 days!
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