I always start by preheating my oven to 375°F so it's fully hot by the time my crumble is ready to bake. While that's heating up, I lightly grease my 9x13-inch baking dish with butter or a light spray of oil. Getting this step done early keeps the rest of the process moving smoothly.
In a large bowl, I toss together the diced pears, chopped cranberries, sugar, cornstarch, orange zest, and cinnamon until everything is evenly coated. Then I pour in the orange juice and give it one more good stir. This step is where all that beautiful tart-sweet flavor starts to develop.
Once the fruit mixture looks well combined, I pour it straight into my prepared baking dish and spread it out into an even layer. I like to press it down just slightly so it bakes evenly and there are no gaps once it's in the oven.
In a separate bowl, I whisk the flour, baking powder, salt, granulated sugar, and brown sugar together until there are no lumps.
I pour the melted butter over the dry topping mixture and stir it with a fork until it forms clumps of varying sizes, some as small as peas and some a bit bigger. This clumpy texture is what gives the topping that irresistible crisp, crumbly bite once baked.
I take handfuls of the buttery crumble mixture and scatter it evenly over the fruit filling, covering as much of the surface as I can. I don't press it down, I just let it sit loosely so it can bake up craggy and golden.
I slide the pan into the oven and bake for 40 to 45 minutes, until the topping turns a deep golden brown and the fruit filling is bubbling up around the edges. My kitchen smells incredible by this point, which is always a good sign.
Once it's out of the oven, I let the crumble rest for about 15 minutes before serving. This resting time lets the filling thicken up so it holds its shape when scooped. I serve mine warm, usually with a big scoop of vanilla ice cream melting right on top.