Low-Sugar, High-Protein Lemon Raspberry Muffins. Berries are finally in season! Pick up a pint, and make these moist and naturally sweet muffins. Made with Greek yogurt instead of buttermilk, they're a tasty way to get some protein without all the fat. These are so light and summery, with bursts of juicy raspberries ??? perfect to grab with your morning smoothie or to bake up for a weekend brunch.