7 tablespoons cold unsalted butter, cut into chunks
Steps
Preheat the oven to 375 degrees F (190 degrees C).
Place plums in a baking dish. Add 1/4 cup sugar, orange zest, orange juice, cinnamon, and nutmeg; toss to mix.
Bake in the preheated oven for 5 minutes.
Meanwhile, combine flour and salt in a mixing bowl. Add chilled butter and rub it in with your fingertips until the mixture resembles bread crumbs. Stir in remaining sugar.
Remove plums from the oven and scatter topping evenly over top. Return to the oven and bake until golden brown, 25 to 30 minutes. Serve hot.