Preheat and prep: Heat your oven to 375°F (190°C). Lightly butter a 9-inch square baking dish or a 2-quart casserole dish.

Make the cherry filling: In a large bowl, combine 6 cups pitted cherries, 1/2 cup granulated sugar, 2 1/2 tablespoons cornstarch, 1 tablespoon fresh lemon juice, 1/2 teaspoon lemon zest, and 1/4 teaspoon almond extract. Toss until the fruit is evenly coated and the cornstarch disappears. Pour into your prepared baking dish and spread in an even layer.

Mix the crumble topping: In another bowl, stir together 1 cup old-fashioned oats, 3/4 cup all-purpose flour, 1/2 cup packed brown sugar, 1/2 teaspoon salt, and 1/2 teaspoon ground cinnamon (optional). Add 1/2 cup sliced or slivered almonds.

Cut in the butter: Dice 1/2 cup (1 stick) cold unsalted butter into small cubes. Add to the dry mixture and use your fingers or a pastry cutter to work it in until you have clumps and sandy bits. If you like, add 1/2 teaspoon vanilla to bring the crumbs together slightly. The texture should hold when pressed but still be crumbly.

Top the fruit: Sprinkle the crumble evenly over the cherries, leaving a few small gaps to let steam escape. Don’t press it down too firmly; a loose layer bakes up crisper.

Bake: Set the dish on a rimmed baking sheet to catch drips. Bake 35–45 minutes, until the topping is deep golden and the cherry juices are bubbling thickly around the edges. If the top browns too quickly, tent with foil for the last 10 minutes.

Rest before serving: Let the crumble cool at least 20–30 minutes. This helps the juices thicken so your servings aren’t runny.

Serve: Spoon warm crumble into bowls. Add ice cream or whipped cream if you like. A sprinkle of extra almonds on top is a nice touch.