Add ground beef, onions, yogurt, red pepper powder, black pepper, and salt into a food processor and blend until completely smooth and fully combined.
Place the blended beef mixture between two sheets of parchment paper and roll out evenly into a thin, flat sheet using a rolling pin.
Peel back the top sheet of parchment and roll the flattened beef tightly into a log shape, pressing the seam firmly closed.
Place the beef roll seam-side down on a baking tray and arrange halved tomatoes and green peppers around it.
Bake in a preheated oven at 400°F (200°C) for 25 minutes until cooked through and golden-brown on the outside.
Remove from oven and let the beef roll rest for 3–5 minutes before slicing.
Toast flatbread or flour tortilla in a dry skillet over medium heat for 30–60 seconds per side until warm and lightly golden.
Slice the beef roll, layer onto the toasted wrap with roasted tomatoes and green peppers, roll up, and serve immediately.