Preheat oven to 350 F (180 C)
Spray a 9 inch (23 cm) square pan with cooking spray. In a medium bowl, combine flour and brown sugar. Cut in butter until mixture is crumbly. Press into pan. Bake until lightly browned, 12 to 15 minutes. Cool slightly.
In a medium bowl, whisk eggs just until blended. Stir in remaining ingredients. Spread over base. Bake until topping is set but still soft in centre, 40 to 45 minutes. Cool completely on a wire rack. Cut into squares. Keep refrigerated.