Preheat oven to 375 degrees F. Spray a 2 quart (or 8 x 8 inch) baking dish with nonstick cooking spray.
Add flour, sugar and butter to a medium-sized bowl.
Using a pastry cutter (or a fork, knife or clean hands), cut cold butter into pea sized pieces into the flour and sugar. Set aside.
Combine blueberries, lemon juice and salt. Add to prepared dish.
Sprinkle crumble topping evenly over top blueberries.
Bake for 45 minutes or until lightly golden brown.
Serve with ice cream or whipped cream, if desired.