Armenian Shish Kebab

Name: Armenian Shish Kebab
Ingredients: 1 1/2 pounds leg of lamb or top sirloin; 2 large onions cut into wedges (for skewers or use pearl onions (sometimes found in the freezer section)); 1 medium onion thinly sliced (for the marinade); 2 teaspoons minced garlic; 1/4 cup tomato paste; 1/2 cup red wine (or substitute 1/4 cup red wine vinegar and 1/4 cup water); 2 tablespoons red wine vinegar; 1/4 cup extra virgin olive oil; 1 1/2 teaspoons salt; 1 teaspoon allspice; 1/4 teaspoon black pepper; 1/2 teaspoon sumac (optional); 1/2 teaspoon aleppo pepper (or substitute 1/2 teaspoon paprika and 1/8 teaspoon of ground red pepper)