Step 1

Position a rack in the center of the oven and preheat to 375 degrees F. Coat a 9-inch round or square cake pan with nonstick baking spray; line the bottom with parchment. Set aside.

Step 2

Beat the butter with the sugar and vanilla in a stand mixer fitted with the paddle attachment on medium-high speed until the mixture is pale and fluffy, about 4 minutes (see Cook's Note). Reduce the speed to medium-low and add the eggs, one at a time, beating for 45 seconds after each addition. Scrape the sides and bottom of the bowl with a rubber spatula.

Step 3

Whisk together the flour, baking powder and salt in a small bowl until combined.

Step 4

With the stand mixer running on low speed, add the flour mixture and buttermilk, alternating between the two, starting and ending with the flour and mixing until just combined. Do not overmix. Pour the batter into the prepared pan and level the top with a rubber spatula.

Step 5

Bake, rotating the pan halfway through, until a toothpick inserted into the center of the cake comes out clean, about 45 minutes. Let the cake cool in the pan for at least 15 minutes before removing it from the pan.

Step 6

For chocolate cake: Add 1/4 cup unsweetened dark cocoa powder to the flour mixture. After the eggs are incorporated, beat in 4 ounces melted and cooled bittersweet chocolate, beating until combined. Alternate adding 1/4 cup of hot brewed coffee with the flour mixture and buttermilk.

Step 7

For lemon poppyseed cake: Beat 2 tablespoons freshly grated lemon zest with the butter, sugar and vanilla. Add 2 tablespoons fresh lemon juice to the buttermilk before it goes into the batter. Before pouring the batter into the cake pan, gently fold in 2 tablespoons poppy seeds using a rubber spatula. For a lemon glaze, whisk 2 tablespoons fresh lemon juice and 3/4 cup confectioners' sugar in a small bowl until smooth. Add more lemon juice, a few drops at a time, if needed. Once the cake is completely cool, drizzle the glaze over the top.

Step 8

For coffee cake: To make a streusel, combine 1/2 cup all-purpose flour, 1/4 cup dark brown sugar, 2 teaspoons ground cinnamon, 1 teaspoon kosher salt and 3 tablespoons cold unsalted butter cut into small cubes in a medium bowl. Use your fingers to rub the butter into the dry ingredients until the mixture looks like coarse sand. Pour half of the batter into the cake pan and spread it out evenly with a rubber spatula. Sprinkle half of the streusel over the batter. Spread the remaining batter on top and sprinkle the remaining streusel over it. For a maple glaze, whisk 2 tablespoons pure maple syrup with 1 teaspoon water and 3/4 cup confectioners' sugar into a small bowl until smooth. Add more water, a few drops at a time, if needed. Once the cake is completely cool, drizzle the maple glaze over the top.

Step 9

For confetti cake: Increase the vanilla extract from 1 tablespoon to 2 tablespoons. Before pouring the batter into the cake pan, gently fold in 1/4 cup rainbow sprinkles using a rubber spatula.

Step 10

For raspberry jam swirl cake: Bring 1/2 cup seedless raspberry jam to room temperature and stir it vigorously with a spoon until smooth. Pour half of the batter into the cake pan and spread it out evenly with a rubber spatula. Place 4 dollops (about half) of the jam on the batter. Spread the remaining batter over top and make 4 more dollops over the batter with the remaining jam. Drag a long wooden skewer through the batter, making sure the skewer reaches down to the bottom of the pan, creating swirls of jam.