Yellowest Yellow Cake With Fudgy Chocolate Frosting

Ingredients

• 1/2 cup strong, cold coffee, plus more as needed
• 1 tablespoon baking powder
• 1/4 teaspoon ground turmeric
• 3 cups all-purpose flour, plus more for the pan
• 1 cup natural cocoa powder
• 3/4 cup canola oil
• 4 1/2 cups powdered sugar
• 4 1/2 teaspoons vanilla extract
• 2 large egg yolks
• 2 large eggs
• 2 cups buttermilk, room temperature
• 2 cups granulated sugar
• 3/4 cup unsalted butter, melted and cooled slightly
• 1 1/2 teaspoons vanilla extract
• 3/4 teaspoon kosher salt
• 1 1/2 teaspoons kosher salt
• 1/4 cup unsalted butter, cold, cubed, plus more for the pan