In pot, simmer tomato sauce with 1/2 tbsp. Italian seasoning. In bowl, combine beef, onion and remaining seasoning. Season with salt and pepper; form into 8 patties. In skillet, cook patties over medium until browned, 3 minutes per side. Top slider bottoms with tomato sauce, a patty, cheese and pepperoni; broil to melt cheese. Add basil and slider tops.