Preheat the oven to 400° F. Coat a muffin pan with cooking spray or line with paper cups.

Place the granola in a heavy-duty plastic bag and crush it lightly with a rolling pin or other heavy object to break up any large clumps. Set aside.

In a large bowl, combine the whole wheat flour, all-purpose flour, baking powder, baking soda and salt. Mix until blended.

In a medium bowl, whisk together the grape juice, egg, oil, sugar and lemon zest until incorporated. Add this wet mixture to the dry ingredients, blend and stir with a rubber spatula until homogenized. Fold in the blueberries.

Fill the prepared muffin cups about two-thirds with batter. Sprinkle with the granola and pat it in lightly so that it adheres.

Place the muffin pan in the oven and bake until the tops are golden brown and a cake tester inserted in the center comes out clean, about 20-25 minutes. Let cool in the pan for 5 minutes.*

Run a small knife around the edges and turn the muffins out onto a wire rack to cool slightly. Serve at room temperature.