INGREDIENTS
1
18-oz. box vanilla cake, plus ingredients called for on box
Juice and zest of 1 1/2 lemons, divided, plus more zest for garnish
1 3/4 cups
fresh blueberries, divided
3 tbsp
all-purpose flour
1 cup
(2 sticks) butter, softened
3 cups
powdered sugar
1/4 cup
heavy cream
1 tsp
pure vanilla extract
pinch of kosher salt
2
thin lemon slices, for topping