Follow these simple steps to create the amazing Nectarine Crumb Tart:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9-inch tart pan.
2. Prepare the Crust: In a mixing bowl, combine the flour, granulated sugar, and salt. Add the cold butter and mix until the mixture resembles coarse crumbs. Stir in the egg and vanilla extract until combined.
3. Press the Dough: Press the dough into the bottom and up the sides of the prepared tart pan. Prick the bottom with a fork to prevent bubbling.
4. Pre-bake the Crust: Place the crust in the preheated oven and bake for about 15 minutes or until lightly golden. Remove from the oven and let it cool slightly.
5. Prepare the Filling: In a separate bowl, toss the sliced nectarines with lemon juice, ground cinnamon, and brown sugar until well-coated.
6. Prepare the Crumb Topping: In another bowl, combine rolled oats, brown sugar, and chopped pecans (if using). Add melted butter and mix until crumbly.
7. Assemble the Tart: Spread the nectarine mixture evenly over the pre-baked crust. Top with the crumb mixture, spreading it evenly across the fruit.
8. Bake the Tart: Return the tart to the oven and bake for an additional 30-35 minutes or until the topping is golden brown and the nectarines are bubbly.
9. Cool the Tart: Remove from the oven and allow the tart to cool in the pan for about 15-20 minutes before slicing.
10. Serve: Carefully transfer the tart to a serving platter.

These steps will guide you in creating this incredible Nectarine Crumb Tart effortlessly!