Preheat oven to 375°F (190°C) with a rack in the center position. Line a muffin pan with paper liners (this recipe yields 9 muffins) or lightly grease with baking spray. Set aside.
In a medium bowl, whisk together the whole wheat flour, all purpose flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, beat the softened butter and sugar with a hand-held mixer. Add the egg, Greek yogurt, apple sauce, and lemon zest and beat until smooth.
Add the dry flour mixture to the wet ingredients and mix together until the flour has just been absorbed. It will be thick and dough-like in texture. Gently fold in the blueberries. Distribute the batter evenly among 9 muffin cups and sprinkle sliced almonds onto the top of each muffin.
Bake for 12 to 16 minutes or until golden brown and toothpick inserted comes clean. Place on rack and let the muffins cool in the pan for 5 minutes. Remove from the pan and transfer to a rack. Serve slightly warm with butter.