Preheat oven to 350 degrees. Butter and flour a 9 x13-inch baking pan. Make topping: In a small bowl combine sugar and cinnamon. Using a fork, blend butter into sugar mixture until it forms large crumbs.
Make cake: In a standing electric mixer or with a hand mixer, cream together butter and sugar. Add egg and mix well. Add flour, baking soda, yogurt, vanilla and zest. Mix on medium for 4 minutes. Pour batter into prepared pan and sprinkle top with blueberries. Lightly press them into batter, if needed. Top with crumble topping. Bake for 45 minutes. Cool on a rack and carefully unmold.
Yield: 9 x13 inch cake