Preheat oven to 350°F (177°C). Butter an 8 x 8-inch baking dish; set aside.
Prepare Topping:
Whisk together flour, brown sugar, cinnamon, and salt in a medium bowl.
Stir melted butter into flour mixture, pressing it together until it clumps. Set aside for 10 minutes.
Prepare Filling:
Combine nectarines, sugar, lemon juice, cornstarch, cinnamon, cardamom, and salt in a large bowl. Mix well.
Assemble + Bake Crumble:
Transfer nectarine mixture to prepared baking dish, spreading in an even layer. Scrape any juices / sugar that remains in bowl into baking dish.
Using hands to crumble topping over nectarines.
Bake until topping is browned and nectarine filling is bubbling, about 45 to 50 minutes.
Let cool at least 30 minutes, then serve plain or topped with ice cream. Enjoy!
Notes
Because nectarines bruise easily, I recommend buying an extra nectarine or two. That way, if you have cut away some of the fruit, you won't run short.I used light brown sugar, however dark brown sugar would also work.For a vegan / dairy free crumble, use plant based butter.If you'd prefer an oat-based topping, feel free to substitute my Oat Crumble Topping. The dessert is delicious either way!Check out the info before this recipe card for helpful tips, variations, related recipes, and more!