1. Preheat oven to 350°.
2. Weigh or lightly spoon flours into dry measuring cups; level with a knife. Combine flours, baking powder, and salt in a small bowl. Combine oil, milk, agave, rind, juice, and egg in a large bowl, stirring with a whisk. Add flour mixture to oil mixture, stirring just until moist.
3. Spoon batter evenly into 12 miniature muffin cups coated with cooking spray. Bake at 350° for 12 minutes or until a wooden pick inserted in center of muffins comes out clean. Remove muffins from pan; cool on a wire rack.