Strawberry Rhubarb Coffee Cake

INGREDIENTS

• Filling:
• 2/3 cup sugar
• 1/3 cup cornstarch
• 2 cups chopped rhubarb
• 1 (10 ounce) package frozen sliced strawberries, thawed
• 2 tablespoons lemon juice
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• Cake:
• 3 cups all-purpose flour
• 1 cup sugar
• 1 teaspoon baking powder
• 1 teaspoon baking soda
• 1 cup cold butter or margarine
• 2 eggs
• 1 cup buttermilk
• 1 teaspoon vanilla extract
• Topping:
• 3/4 cup sugar
• 1/2 cup all-purpose flour
• 1/4 cup cold butter or margarine