Buttered Oat Cake with Summer Fruits

Makes one 9" cake

This is a cake meant to be eaten over the course of many warm summer days, sliced off in thick or thin pieces, either slathered with softened butter or on top of a napkin while standing in your kitchen in a bathing suit. It’s got a just-sweetened flavor with a crumb that could almost be described as porridge-y, thanks to all the oats, which hydrate so much while baking they almost disappear. Use fresh or frozen fruit, berries, stone fruit or a mix of all. It’s flexible, and one of the best things here is that because oats can really handle a lot of liquid absorption, it’s a great place to put your juicer fruits to work.

Two pieces of advice that will make your cake more successful. 1: The cake is on the taller side, so bake it longer than you think (the top will get nice and dark, the oats will toast, the sugar will caramelize, three cheers!). 2. Make sure this cake is cooled to room temperature before slicing, otherwise it will crumble and not slice well at all (I am speaking from personal experience).

Ingredients

• Cooking spray
• 1 cup/145g all-purpose flour
• 1 ¼ cups/110g plus ¼ cup/25g rolled oats
• 2 teaspoons baking powder
• 1 teaspoon kosher salt
• 1 stick/4 ounces/115g unsalted butter
• ½ cup/100g light brown sugar
• ¼ cup/50g plus 3 tablespoons granulated sugar
• 1 teaspoon vanilla extract
• 2 large eggs
• ¾ cup/180ml buttermilk or thin yogurt (not greek yogurt)
• 1 pound blueberries or blackberries, fresh or frozen (or one pound cherries, peaches or plums, pitted and chopped)
• Turbinado or demerarra sugar, for sprinkling

Preparation

1. Preheat the oven to 350°F. Spray the bottom of a 9-inch cake pan with cooking spray and line with parchment paper (either cut to fit the bottom, or leaving some hanging over the edges for easy removal).
2. In a medium bowl, whisk the flour, 1 ¼ cup oats, baking powder, and salt together.
3. In a stand mixer fitted with the paddle (or in a large bowl with an electric hand mixer), beat the butter, brown sugar, ¼ cup granulated sugar, and vanilla together on medium-high, periodically scraping down the sides of the bowl to make sure everything incorporates, until the mixture is pale, light, fluffy, and creamy, about 5 minutes.
4. Add the eggs, one at a time, beating to blend after each addition. (This is a good time to scrape down the sides again.)
5. Reduce the mixer speed to low and carefully add half the oat mixture, followed by half the buttermilk. Repeat with the remaining flour mixture and buttermilk, beating just until no large lumps remain.
6. Using a spatula, gently fold in about ¾ the fruit and transfer the batter to the prepared cake pan. Scatter with the remaining fruit and sprinkle with remaining ¼ cup oats and 3 tablespoons granulated sugar. Bake until the cake is puffed, deeply golden brown, and pulling away at the sides, 65–75 minutes. (It should spring back slightly when pressed in the center and appear fully baked, especially in the center, where the fruit meets the cake.)
7. Let the cake cool completely (really, all the way) before slicing.

DO AHEAD: Cake keeps well for 5 days at room temperature, is also nice chilled, stored up to 5 days.