Preheat your oven to 350°F (175°C) and grease a baking dish with butter or non-stick spray.
In a large mixing bowl, combine sliced peaches with lemon juice, cinnamon, cayenne (if using), and half of the sugar. Toss gently until the peaches are evenly coated and set aside so their juices start to release.
In a separate bowl, mix oats, flour, remaining sugar, and vanilla extract. Add the cold butter pieces and use your fingers or a pastry cutter to work the butter into the dry ingredients until the mixture resembles coarse crumbs.
Spread the spiced peach mixture evenly into the prepared baking dish, smoothing the top with a spatula.
Sprinkle the crumble topping evenly over the peaches, pressing it down slightly to adhere.
Bake in the preheated oven for 35-40 minutes, or until the topping is golden brown and bubbling around the edges.
Remove from the oven and let cool for a few minutes. The aroma of cinnamon and baked fruit will fill your kitchen.
Serve the warm peach crisp with a scoop of vanilla ice cream or a dollop of whipped cream for extra indulgence.
