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Preheat oven to 375 degrees and grease a 9" circular cake pan or an 8x8 square baking pan.
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In a small bowl, mix together flour, sugar, lemon zest, baking powder, cinnamon, all spice and salt.
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In a separate mixing bowl, lightly mix together oil, egg, vanilla extract, and milk.
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Make a well in the center of dry ingredients, and pour wet ingredients into it. Stir gently, as to not over stir the mix.
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Once just combined, fold in chopped apples and blueberries. Pour into your pan and set aside.
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In a small bowl, mix together the topping ingredients until combined. Sprinkle evenly over the top of the batter in the pan. Use a rubber spatula to swirl the topping.
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Bake for 25 minutes or until your cake tester comes out clean.
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While the cake is cooling, make the icing by stirring together the powdered sugar, vanilla extract and milk. Drizzle over the top of the coffee cake.
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Serve warm, or cool.