In a large bowl, combine water, yeast, honey and olive oil. Mix with a spoon, then let sit until foamy, about 10 minutes. Add in 2 1/2 cups flour, garlic powder and salt, stirring with a spoon until the dough comes together but is still sticky. Using your hands, form the dough into a ball and work in the additional 1/2 cup flour, kneading it on a floured surface for a few minutes. Rub the same bowl with olive oil then place the dough inside, turning to coat. Cover with a towel and place in a warm place to rise for about 1 to 1 1/2 hours.
After the dough has risen, punch it down and place it back on the floured surface. Using a rolling pin or your hands, form it loosely into your desired shape Place the towel back over the dough to rest.
While the dough is resting, preheat your grill to the highest setting. At this point, you can make the butter and slice the tomatoes.
Roll the dough out into a circle (or whatever shape! I never worry about a perfect circle on the grill.). Generously flour your pizza peel and place the dough on the peel, then immediately take it to the grill. Brush or spray the top of the dough with olive oil.
Quickly and gently use a spatula or additional pizza peel to slide your pizza directly on to the grill grates. I like to turn off the heat directly under the dough to help the crust from burning. Close the lid and cook until the pizza dough is bubbly and golden on one side, anywhere from 3 to 5 minutes. Flip the dough and grill the other side for 2 to 3 minutes more.
Slide the dough off the grill with a pizza peel. Spread the garlic herb butter on top of the crust so it melts immediately. Top with the sliced tomatoes right after, so they get a bit warm too. Sprinkle the tomatoes with flaked salt and additional herbs. Slice and serve!