About 15 minutes before you would like to start cooking your pizza, heat two tablespoons of olive oil on medium. Add the onion and defrosted spinach. Cook for 10-15 minutes, stirring often. The longer you cook the vegetables, the softer and sweeter they will become.
While the vegetables are cooking, put ½ cup of shredded cheese in a small bowl and 1 tablespoon of extra virgin olive in a small dish/ container to bring to the grill. About 10 minutes into cooking the vegetables, heat grill to 400 to 450 degrees.
When the vegetables are cooked, place the pizza shell on a cookie sheet. Brush the top side of pre-cooked pizza dough with 1 tablespoon of olive oil.
When you go out to the grill, you should have:
Place on the hot grill the pizza shell with the side brushed with olive oil on the grill. Set the timer for 2 minutes. Quickly brush the top of the shell with the other Tablespoon of olive oil and cover the grill. When the timer goes off, turn the dough with the fork or tongs. Immediately spread the cooked vegetables over the dough using a spatula. Sprinkle with the shredded cheese.
Set the timer for 3 minutes and cover the grill. Check at 3 minutes; if the cheese has not melted, use the tongs to check to see if the bottom is not burning. If it is not, cover and cook for 30 seconds to 1 minute more. The cheese should be melted but the shell not burned.