Preheat oven to 350 degrees. In a standing mixer, combine melted butter and both sugars on medium high speed for 2-3 minutes.
Melt ¼ cup of the white chocolate chips (30 seconds at a time in the microwave), and then add to the standing mixer. Mix on medium high speed until completely combined.
In a separate bowl, whisk together flour, baking powder, and salt. Set aside.
Add egg, vanilla extract, almond extract, and lemon zest to standing mixer and mix until well combined. Add flour mixture to the standing mixer and stir on lowest speed until just barely combined (hardly any flour pockets left). Don't overmix.
Add remaining ¾ cup white chocolate chips and mix in by hand with a rubber spatula. Then mix in 1 cup of frozen raspberries***. Don't overmix, you can more evenly distribute the raspberries when placing in the pan.
In an 8x8 square pan, line with parchment paper extending over the edges. Gently press the batter into the pan, evenly distributing throughout.
Bake for 35-40 minutes, until the edges start to turn a golden brown and the center has set. Rotate halfway through baking. Let sit in pan for an additional 20 minutes before removing so that it can continue to set.
Melt the melting chocolate in the microwave, 30 seconds at a time. Drizzle over the top. Enjoy!