Step 1

Adjust the oven rack to the middle position and heat the oven to 350 degrees F—Pour 4 tablespoons of melted butter into a 3.1-quart nonstick rectangle cake pan, tilting to coat the bottom and sides. Whisk 3/4 cup light brown sugar, 1 teaspoon cornstarch, 1 teaspoon pure almond extract, and 1 teaspoon pure vanilla extract together in a small bowl, then sprinkle evenly over the melted butter. Arrange pitted cherry over the sugar mixture, nesting cherries snugly together.

Step 2

Sift together the flour and baking powder in a large bowl; set aside. Place the 1/4 cup avocado oil, 1 stick unsalted butter, 1/4 teaspoon kosher salt, 1 cup granulated sugar, and 1/2 cup light brown sugar in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed for about 3 minutes. Beat in the vanilla and almond extracts.

Step 3

Beat in the eggs and egg yolk one at a time, ensuring they emulsify completely with the butter mixture. Reduce the mixer speed to low, scrape bowl and beater and add 1/2 of the dry ingredients, and add half the buttermilk and beat until just combined.

Step 4

Next, add the remaining flour mixture and the buttermilk, and beat on low speed until just combined. Do not overmix the batter! Using a rubber spatula, fold it all by hand to ensure no lumps at the bottom of the bowl. Pour batter over the cherries in the pan and smooth the top with a rubber spatula.

Step 5

Bake the Cherry Upside-Down Cake until deeply golden brown and a toothpick inserted in the center comes out clean, 50 to 55 minutes. Let the cake cool in the pan on a wire rack for 5 minutes. Run a knife around the pan's edge to loosen the cake's sides, then invert the cake onto a serving platter. Discard parchment paper. Let the cake cool for a least 1 hour. Serve warm or cool—store covered in the refrigerator for up to 3 days.