With oven rack on the middle setting, preheat oven to 350º. Line a 9x9 inch baking pan with foil or parchment paper, with enough hanging over the sides that you can use them as handles to remove the brownies easily when the time comes. Set aside.
Using an electric stand mixer fitted with paddle attachment, or handheld mixer and large bowl, stir together flour, sugar and salt until well combined. Add the butter and mix until well combined, at a medium speed. You do not want to beat at high speed or it will incorporate too much air.
In a separate, small bowl, whisk the eggs, lemon zest and extract together. Add to your batter using a rubber spatula to scrape it all out. Mix on low speed until well blended and smooth, scraping down sides of bowl as necessary. Alternately, you may stir by hand using a rubber spatula until well blended and smooth.
Push batter into prepared pan and smooth the top. Add raspberries throughout the batter, and push down slightly so they are in the batter, versus just sitting on top. Though some on top is fine, too! Bake in preheated oven until golden brown around the edges and firm to the touch in the center, about 25-30 minutes. (It took mine 30 minutes, but will vary by oven.) Don't overcook or the brownies will be dry. Mine were nice and ooey gooey! Transfer to wire rack and allow to cool at least 1 hour before removing from pan. Cool completely before spreading on glaze.
Use the baking parchment on sides of pan to lift brownie cake out and transfer to cutting board. Once the brownie cake is completely cool, prepare the glaze.
In a medium bowl, whisk together sugar, lemon juice and zest until smooth and creamy. Pour glaze over cooled brownie cake and spread evenly over the top.
Allow glaze to dry slightly on the surface before adding sprinkles and cutting. The brownies can be stored in an airtight container at room temperature or in the refrigerator. Brownies will keep airtight at room temperature or in the refrigerator for up to 1 week, or in the freezer* for up to 6.