Preheat oven to 350℉/176℃. Line an 8x8 pan with parchment paper and set aside.
In a large bowl (this is the bowl you'll be using for the entire bake so make sure it is large!), add the brown sugar and lemon zest. Using your fingers, rub them together for 2 minutes. This is going to release the lemon oils and fragrance.
3/4 cups light brown sugar, zest of 1 lemon
Add in melted butter and whisk in.
1/2 cup unsalted butter
Add in lemon juice, egg, and vanilla. Whisk until well combined.
1 egg, 1 tbsp lemon juice, 1 tbsp vanilla
Add in flour, baking powder, and salt. Gently mix with a spatula until a soft batter forms.
1 1/4 cups all-purpose flour, 1/2 tsp baking powder, 1/4 tsp salt
Toss in raspberries and mix in a few times. Don't over-mix!
3/4 cups raspberries
Transfer into the prepared pan and spread evenly. Add extra raspberries on top.
Bake for 25-28 minutes or until the edges are a golden brown and the middle is slightly puffy. A toothpick inserted will come out clean.