Preheat the oven to 190C.
Line a square 20cm baking pan with parchment paper. Butter the sides and bottom of the lined pan. Set aside.
In a medium mixing bowl, stir together cherries, cornstarch and lemon juice.
In a large mixing bowl, stir together melted butter and sugar. Add flour, baking soda, baking powder and salt and stir with a fork until the mixture resembles crumbs.
Reserve 3/4 cup of mixture.
Press remaining crumb mixture into the bottom of the pan. Spread cherry filling over the crust.
Sprinkle remaining crumb mixture over cherries.
Sprinkle sugar over crumb topping. Bake bars for 23 to 25 minutes OR until the top is golden.
Let them cool completely before cutting.