Preheat the oven to 350°F. Spray a 9×5-inch loaf pan with non-stick spray and set aside.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda and salt. Set aside.
In a medium bowl, whisk together the yogurt, oil, egg, egg whites, and lemon zest. Add the wet ingredients to the flour mixture and stir just until moistened. Gently stir in the raspberries.
Pour the batter into the prepared pan and bake for 50 minutes, or until a toothpick inserted in the center of the loaf comes out clean. Cool the loaf in the pan for 10 minutes. Then remove it from the pan to a wire rack, and let it cool completely before slicing.
Notes
If the loaf begins to brown during baking, cover the loaf lightly with a piece of foil until finished. This will prevent it from darkening too much.