In a small bowl, whisk together 3 eggs, 2 tsp. (10ml) of vanilla extract and 1/2 cup (125 ml) of melted butter.
Open the jar and pour the contents into a separate mixing bowl.
Using a wooden spoon, stir all dry ingredients together.
Add egg mixture into the dry ingredients from the jar and stir until fully combined.
Spread batter into a greased 8" square baking pan, then bake at 350°F (177°C) for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely before serving.
Note: Eggs should be at room temperature for best results.