Ingredient of Zucchini Layer Cake with Tangy Buttercream Frosting Recipe

For the cake:

• Unsalted butter, for coating the pans
• 3 cups bleached cake flour, such as Softasilk, plus more as needed
• 1 1/2 teaspoons baking powder
• 1 1/2 teaspoons ground cinnamon
• 1 teaspoon baking soda
• 1/2 teaspoon freshly ground nutmeg
• 1/2 teaspoon fine salt
• 4 large eggs, at room temperature
• 1 cup packed dark brown sugar
• 1 cup granulated sugar
• 1 cup vegetable oil
• 2 teaspoons vanilla extract
• 14 ounces zucchini (about 3 to 4 medium zucchini), ends trimmed and grated on the large holes of a box grater (about 3 cups)

For the buttercream frosting and nut filling:

• 4 sticks (1 pound) unsalted butter, at room temperature
• 1 3/4 cups powdered sugar
• 1 tablespoon vanilla extract
• 1/4 teaspoon fine salt
• 1 cup plain whole-milk Greek yogurt, at room temperature
• 2 cups pecans (about 8 ounces), toasted and finely chopped