Cut the chicken breast and beef sirloin into uniform 1-inch cubes.
In a small mixing bowl, whisk together the Greek yogurt, lemon juice, minced garlic, smoked paprika, cumin, sea salt, and black pepper.
Place the meat cubes into a shallow glass dish and coat thoroughly with the yogurt marinade, allowing it to rest for at least 20 minutes in the refrigerator.
While the meat marinates, chop the red bell pepper and red onion into 1-inch pieces suitable for skewering.
Thread the marinated chicken, beef, and vegetables onto skewers, alternating the proteins and produce for even cooking.
Preheat a grill or grill pan to medium-high heat and lightly brush the surface with extra virgin olive oil.
Grill the skewers for 8 to 10 minutes, turning every few minutes until the meat is cooked through and the vegetables show light char marks.
While the skewers are grilling, place the cottage cheese in a small blender or food processor and pulse until completely smooth to create a high-protein dipping sauce.
Remove the skewers from the heat and serve immediately alongside the chilled, creamy cottage cheese dip.