Strawberry Rhubarb Coffee Cake
Adapted from With Love & Butter
Makes one-8 inch cake

In the introduction to this recipe, Holly mentions that you can make this same cake with any fresh or thawed (and drained) frozen fruit.  If you do use another combination (favorites include Raspberry-Peach, Blackberry-Nectarine, and Cherry-Apple), there is no need to cook the fruit.  Just lay it over the cake batter.

Filling
1 1/2 cups thinly sliced rhubarb
2 cups whole strawberries
2 1/4 tsp. lemon juice
5 tbsp. sugar
3 3/4 tsp. cornstarch
1/4 tsp. nutmeg

Streusel Topping
1/2 cup flour
1/3 cup brown sugar, firmly packed
1/4 tsp. cinnamon
Pinch of salt
1/4 cup cold butter (1/2 stick), sliced
3 tbsp. old fashioned oats (not quick or instant)

Cake
1 1/2 cups flour
1/2 cup sugar
1/2 tsp. baking soda
1/2 tsp. baking powder
1/4 tsp. salt
1/2 cup (1 stick) cold butter, sliced
1/2 cup buttermilk
1 egg
1/2 tsp. vanilla

Make the filling: Combine the rhubarb and strawberries in a saucepan and cook for 5 minutes over medium heat.  Sprinkle with the lemon juice.  Stir together the sugar, cornstarch, and nutmeg.  Distribute over the fruit, stir and reduce the heat to medium-low.  Cook, stirring often to prevent sticking, until the rhubarb is tender and the liquid has thickened.  Set aside.  The filling can be used immediately or stored in the refrigerator for up to 2 weeks.

Make the streusel topping: Place the flour, brown sugar, cinnamon, salt, and butter in a food processor fitted with the steel knife blade.  Pulse to cut in the butter and make a nice sandy-textured topping.  Don’t over-process.  Stir in the oats by hand and set aside.  Reassemble the food processor without washing.

Preheat the oven to 375°F with the rack in the center position.  Butter an 8-inch square baking dish.

Make the cake layer: Place the flour, sugar, baking soda, baking powder, salt, and butter in the food processor bowl.  Pulse until the butter is reduced to BB-sized bits and the mixture is dry and crumbly.  Scrape into a bowl  Whisk the buttermilk, egg, and vanilla in a small bowl and add to the dry mix.  Stir just until a dough forms.

Assemble the cake:  Spread the batter evenly in the pan and cover with the strawberry rhubarb filling.  Distribute the streusel topping over the fruit.  Bake the coffee cake for 50-60 minutes, or until no gooey batter shows when you probe into the cake.  Cool the cake for at least an hour before serving.