Bring a pot of water to a boil. Prepare a large bowl of ice water.
Use a paring knife to cut a small “X” in the bottom of 4 large nectarines. Place the nectarines in boiling water for 30 seconds, followed by ice water for 2 minutes.
Gently peel the skin away from the nectarines. Remove the pits from the nectarines and cut into 1-inch pieces.
Place the nectarine pieces into an 8x8-inch dish (no need to grease it) and sprinkle with 1 tablespoon lemon juice.
In a large bowl, whisk together 1 cup all-purpose flour, ¾ cup brown sugar, 1 teaspoon cinnamon, and ⅛ teaspoon salt.
Cut ½ cup cold butter into small cubes and add to the flour mixture. Mix with two forks, a pastry blender, or your hands until the mixture resembles wet sand.
Sprinkle the flour mixture over the nectarines. Bake for 25–30 minutes, or until lightly golden brown on top.
Serve warm with a scoop of vanilla ice cream on top.