Summer fruit upside down cake

My parents must think we're severely malnourished because whenever they visit they bring us cartons of fruit from Costco. Most of it ends up spoiling because we can't keep up with the quantity. I found some of our apricots and plums growing fuzz (ew) and figured I should be proactive this time and put the good fruit to use before they too turned green and furry.

I made David Lebovitz's Upside Down Cake with apricots and plums. The cake is so excessively delicious, it almost feels evil. I can't even describe it. I don't care so much for plain white cake but this recipe, along with the carmelized fruit that gets soaked up into the batter... it's heavenly. I plan to experiment with all different kinds of fruit. Please be forewarned: make this cake for guests, or else you will end up eating it all by yourself in one sitting. Seriously. It's amazing fresh out of the oven, but just as incredible (or maybe moreso) the next day when things have really soaked in.

Lebovitz used a 10" cast iron skillet but I used a plain old 9" cake pan and it worked out fine. Way beyond fine.

Upside Down Cake
Adapted from David Lebovitz

One 9-inch (25cm) cake, 8-10 servings

You have some latitude with the fruits that you use. Just make sure that whatever you use covers the bottom in a substantial layer, around double-thickness, since the fruit will cook down while baking and settle nicely into place. Berries and such as good nestled in the gaps between the slices of fruits.

For the fruit layer:

3 tablespoons butter (45g), salted or unsalted
3/4 cup packed (170g) light brown sugar
fruit: About 4-5 plums sliced 1/2" thick, 4-5 apricots quartered, or whatever fruit you desire

For the cake layer:

8 tablespoons (115g) unsalted butter
3/4 cup (150g) sugar
1 teaspoon vanilla extract
2 large eggs, at room temperature.
1 1/2 cups (210g) flour
1 1/2 teaspoon baking powder, preferably aluminum-free
1/4 teaspoon salt
1/2 cup (125ml) whole milk, at room temperature

Melt the 3 tablespoons (45g) of butter in the cake pan over low heat. Add the brown sugar and cook while stirring, until the sugar is melted and begins to bubble. Remove from heat and let cool.

Once cool, arrange the fruit in a pinwheel design.

To make the cake, preheat the oven to 350F. (190C)

Beat the 8 tablespoons 9115g) of butter and sugar until fluffly. Add the vanilla, then the eggs, one at a time, until smooth.

Whisk or sift together the flour, baking powder, and salt.

Stir in half of the flour mixture, then the milk, then the remaining dry ingredients. Do not overmix: stir just until the flour is barely incorporated into the batter.

Spread the batter over the fruit, then bake for 45 minutes to one hour (depending on the size of the pan, and the thickness of the batter.) The cake is ready when it begins to pull away from the sides of the pan and the center feels just set.

Remove from oven, let cool about 20 minutes, then place a cake plate on top, and wearing oven mitts, flip the cake out on to the plate, taking care, as there may be some hot caramel that might escape.

Serving: Upside Down Cake is best served warm, perhaps with whipped cream or vanilla ice cream. It can be made in advance, left in the pan, and rewarmed in the cake pan or skillet right before serving. It's also very good rewarmed in a microwave, and served immediately.