Preheat oven to 325 degrees F. Line a 9-inch-by-9-inch square pan with parchment paper. Spray with nonstick baking spray.
In a bowl, add dry ingredients; whisk to combine. Set aside.
Add buttermilk and lemon juice to a measure cup; whisk to combine. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a handheld mixer, cream butter and sugar until light and fluffy, about 1-2 minutes. Add the eggs, one at a time, scraping down the sides of the bowl between additions. Add zest and extract; mix to combine.
Add flour mixture, alternating with buttermilk mixture, until the batter is smooth. Transfer the batter to the prepared baking pan. Bake for 40-45 minutes, or until a toothpick inserted in the center comes out mostly clean. Allow the cake to cool for 30 minutes in the pan. Transfer to a wire rack to cool completely.
To make the frosting, add cream cheese and butter to a stand mixer fitted with a paddle attachment, or in a large bowl with a handheld mixer, and beat until smooth. Slowly add the powdered sugar, mixing until smooth. Add lemon zest, juice, and vanilla extract and mix to combine. Using an offset spatula, frost the cooled cake. Sprinkle your favorite sprinkle mixture over the frosting.