Cook filling: Heat 1 tbsp oil in a skillet. Sauté onion until soft. Add beef or vegetables, cumin, coriander, salt, pepper, and chili (if using). Cook until browned or softened. Cool slightly.
Assemble: Place 1 tbsp filling in the center of each wrapper. Fold into a triangle, sealing edges with water.
Fry: Heat 2 inches of oil to 350°F. Fry sambusas 2-3 minutes per side until golden. Drain on paper towels.