In a medium saucepan, melt 8 tablespoons unsalted butter (1 stick), over medium low heat. Turn the heat onto medium and begin stirring to move the butter around as it starts to melt. Once melted, the butter will begin to foam and sizzle around the edges. Keep stirring to prevent butter from burning. In about 5-8 minutes from when you started, the butter will turn golden brown. The foam will slightly subside and the milk solids on the bottom of the pan will toast and become golden. It will smell intensely buttery and nutty: the desired outcome. Remove from heat once you smell the butter, nutty scent. Allow to cool slightly as you prepare the rest of the crust.

Preheat your oven to 375 degree Fahrenheit. In a medium bowl, stir together your brown sugar, granulated sugar, salt, flour, and vanilla extract until well combined. Add in your brown butter and mix everything together well. Line a baking 9 x 13 baking dish with parchment paper and pour in your crust. Using a spatula, or your fingers, press the mixture into the bottom of your baking dish to form an even crust.

In a medium bowl, combine your fruits with lemon juice, lemon zest, chopped thyme leaves, brown sugar, and cornstarch. Stir together well until the cornstarch dissolves. Pour the fruit mixture onto your prepared crumble crust. Using a spatula spread the mixture evenly across the crust.

In a small bowl, mix together your oats, flour, brown sugar, salt, cinnamon and olive oil until well combined. Sprinkle the crumble topping over your fruit, using your fingers to spread the topping as evenly as possible.

Bake for 45-50 minutes in a 375 degree Fahrenheit oven until the fruit is bubbly and the oat topping is golden. Cool for at least 15 minutes before serving.