Combine all dry ingredients in 9x13 pan.
Drizzle melted butter over dry ingredients, mix well, and press into bottom of pan.
Beat all ingredients until blended. Batter will not be completely smooth.
Pour into unbaked graham cracker crust. Tap bottom of pan against counter to remove air bubbles.
Bake at 350° for 50-55 minutes. Surface will be slightly browned around edges and middle will have set up. Refrigerate uncovered immediately.
Combine raspberries, sugar, and lemon juice in a saucepan over medium heat; cook and stir until raspberries break down, sugar dissolves, and sauce is heated through, 3 to 7 minutes.
Remove from heat and press sauce through a fine-mesh strainer to remove seeds.
Cool to room temperature, cover the bowl with plastic wrap, and refrigerate until chilled, at least 45 minutes.