• Preheat the oven to 400℉/205℃. Line your jumbo muffin tin with liners and set aside.

For the streusel

• Add flour, white sugar, and cold cut up butter into a bowl. Using your hands, mix together until a crumbly, streusel mixture forms. Set in the refrigerator while you make the muffin batter.
  3/4 cup all-purpose flour, 5 tbsp butter, 1/3 cup white sugar

For the muffins

• In a medium-sized bowl, add the dry ingredients. Mix together and set aside.
  2 cups all purpose flour, 2 tsps baking powder, 1 tsp baking soda, 1/2 tsp salt
• In a large bowl, add the white sugar and lemon zest. Using your fingers, rub them together for 2 minutes. This is going to release the lemon oils in the muffins.
  1 cup white sugar, Zest of 1 lemon
• In the same bowl, add the oil, eggs, sour cream, vanilla, and lemon juice. Whisk together until combined and smooth.
  1/2 cup oil, 2 large eggs, 1 tbsp lemon juice, 1 tbsp vanilla, 1 cup sour cream
• Add in the dry ingredients into the wet. Using a spatula, slowly fold until a soft muffin batter forms. Mix until JUST combined.
• Add 1-2 tsps of flour into the bowl with the blueberries and gently toss around until evenly coated. The light coating of flour will help prevent the berries from sinking while they bake.
  1 1/3 cups fresh blueberries*
• Add the blueberries and mix in a few times.
• Evenly divide the batter between the muffin liners. Make sure they are about 3/4s of the way full max, no more or else they will overflow. This recipe made 8 jumbo muffins for me, but depending on the size of your jumbo pan it can make more or less.
• Sprinkle streusel on top.
• Bake the muffins at 400°F for 22-27 minutes. The muffins are ready when a toothpick inserted comes out clean.
• Cool the muffins and enjoy! They are best served fresh and stay good on the counter for 3 days, and in the fridge for up to 1 week.