Preheat oven to 400°F. Coat 12 muffin cups with cooking spray or line with paper liners.
Use a vegetable peeler to remove the zest from the lemon in long strips.
Combine the zest and sugar in a food processor; pulse until very finely chopped. Add buttermilk, oil, egg, and vanilla and pulse again until well blended.
Combine whole-wheat flour, all-purpose flour, baking powder, baking soda, and salt in a large bowl.
Add the buttermilk mixture to the dry ingredients and gently stir just until almost blended. Gently fold in raspberries.
Divide the batter equally among the muffin cups and bake for 20-25 minutes until the edges and tops are golden.
Let cool in the pan for 5 minutes before turning out onto a wire rack to cool completely.
Serve with yogurt on the side.