Preheat oven to 375°F and set one rack to the middle position.

Make the filling: To a large mixing bowl, add strawberries, rhubarb, orange juice and zest, vanilla bean seeds and extract, cornstarch, sugar, and salt.

With a rubber spatula or wooden spoon, toss the ingredients together until the fruit is evenly coated and the sugar begins to dissolve. Set aside.

Make the topping: To a food processor, add flour, granulated and brown sugars, baking powder, and salt. Pulse the food processor just until the ingredients are combined and no lumps remain.

Add the vegan butter, spacing out the cubes over the dry ingredients as best you can.

Continue pulsing until the mixture starts to clump together and you see crumbles forming. Add the pecans and pulse just until they are evenly distributed.

Grease a 9-inch square tin or other 2/2.5-quart baking dish with baking spray or more vegan butter.

Give the fruit mixture a few final stirs to incorporate any juice that has accumulated at the bottom of the bowl. Dump the mixture into the baking dish.

Crumble the topping over the fruit. (Using your hand to clump the topping together, and then breaking it into smaller pieces works great for picture-perfect crumbles.)

Bake for 50 to 55 minutes, or until the topping is deep golden brown and the filling is bubbling up through the crumbs.

Let the crumble cool on a wire rack for about at least 15 minutes before serving.