Sweet! A Cardamom Cake With Coffee Buttercream

Ingredients

• 2 tablespoons ground cardamom
• 3 large eggs
• 2 egg yolks
• 1 tablespoon pure vanilla extract
• 3/4 cup sour cream
• 1/4 cup buttermilk
• 2 cups all-purpose flour
• 1 1/2 cups sugar
• 3/4 teaspoon baking soda
• 3/4 teaspoon salt
• 1/2 pound unsalted butter at room temperature
• 1 pound unsalted butter
• 2 teaspoons pure vanilla extract
• 1/4 teaspoon salt
• 1/4 cup strong coffee
• 3 cups confectioner's sugar