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Preheat oven to 375° F. Grease 9x13 inch baking pan or line aluminum foil sprayed with cooking spray.
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In large bowl, beat butter and sugar with mixer until light and fluffy. Beat in egg and vanilla.
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In medium bowl stir together flour, baking powder and salt.
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Slowly add to butter mixture alternately with milk, beating well after each addition.
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Gently fold in blueberries. Pour into greased baking pan.
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In small bowl, combine the sugar flour and cinnamon. Cut in butter with fork or pastry blender until crumbly
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Sprinkle over top of batter. .
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Bake for approximately 1 hour or until a toothpick inserted in the center comes out clean.
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Cool on a wire rack.
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Serve slightly warm or at room temperature.