Meanwhile, bring 1-1/2 cups blueberries, 1/2 cup sugar and 1 Tbsp. cold water to boil in saucepan, stirring constantly. Dissolve corn starch in 3 Tbsp. of the remaining cold water; whisk into blueberry mixture. Cook on low heat 2 min. or until thickened, stirring constantly. Remove from heat. Add reserved butter; stir until melted. Reserve 1/2 tsp. lemon zest and 1 tsp. juice; stir remaining zest and juice into blueberry mixture. Pour into crust.