Instructions

• Preheat the oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper and spray the parchment and any exposed pan surface with non-stick baking spray. Set the pan aside.
• In a large bowl, sift together 2 3/4 cups all-purpose flour, 2 1/2 teaspoons baking powder, 1/2 teaspoon baking soda, and 3/4 teaspoon salt. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a handheld electric mixer, beat 1 cup (8 ounces) unsalted butter (room temperature) and 2 cups granulated sugar on medium-high speed until light and fluffy, about 3 minutes. Scrape down the sides and bottom of the bowl with a rubber spatula, then beat an additional 30 seconds.
• Add 4 large eggs, one at a time, beating well after each addition and scraping down the sides and bottom of the bowl as needed so everything is evenly incorporated.
• Beat in 1 teaspoon vanilla extract and 1 teaspoon lemon extract until combined.
• With the mixer on low speed, add the sifted dry ingredients and beat just until barely combined, about 20 seconds. Stop while there are still small streaks or lumps of dry ingredients—do not overmix.
• Turn the mixer off. Add 1/2 cup buttermilk (room temperature), 1/2 cup sour cream (room temperature), 1 1/2 tablespoons finely grated lemon zest, and 1/2 cup fresh lemon juice. Turn the mixer on the lowest speed and mix just until the ingredients are incorporated.
• Turn the mixer off and use a rubber spatula to gently fold the batter, scraping from the bottom of the bowl to the top to ensure no pockets of dry ingredients remain.
• Pour the batter into the prepared 9×13-inch pan and use a spatula to smooth the top evenly.
• Bake in the preheated oven for 35 to 40 minutes, until the top is firm, golden brown, and a toothpick inserted into the center comes out clean or with a few moist crumbs attached.
• Place the cake pan on a cooling rack and allow the cake to cool completely in the pan before frosting.
• For the frosting: in the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a handheld mixer, beat 8 ounces very soft cream cheese and 1/2 cup very soft unsalted butter on medium-high speed until completely smooth, about 2 minutes.
• Reduce the mixer speed to low and gradually add 3 cups sifted confectioners’ sugar, mixing until the sugar is incorporated.
• Add 2 1/2 tablespoons fresh lemon juice and 1 teaspoon lemon extract and beat on low until combined.
• Increase the speed to medium-high and beat the frosting for 2 minutes to lighten and smooth it.
• Once the cake has completely cooled, spread the frosting evenly over the top of the cake.
• Cover leftover cake tightly and store in the refrigerator for up to 3 days.