Method:
Preheat oven to 375°F. Butter a 12-cup muffin tin or line with paper muffin liners. In a large bowl, cream together butter or oil and sugar. Stir in applesauce, eggs, orange juice and vanilla.
In a second large bowl, whisk together flour, baking powder, zest and salt. Stir flour mixture into butter-egg mixture until just combined. Gently stir in blueberries. Spoon batter into muffin cups and bake until a toothpick inserted in the center of a muffin comes out clean, about 30 minutes.