Combine warm water and sugar in a mixing bowl. Stir a few times, until sugar dissolves. Sprinkle yeast over the top and let sit for about 5 minutes, until yeast looks frothy and is bubbling. Add in salt, minced garlic, 2 TBSP olive oil and onion powder. Mix until combined. Continue mixing with a dough hook (or kneading by hand) and additional 5 minutes. Cover let sit in a warm place until nearly double in size, about 30-45 minutes.
While you're waiting for the dough to rise, slice tomato thin and set on paper towels to absorb a lot of the moisture.
Preheat oven to 375 degrees F.
Cover a baking sheet with parchment paper. Transfer dough to baking sheet. Dough will be sticky- put a little olive oil on your hands, then gently spread dough out a bit, until it's a rounded 12" oval. Drizzle remaining 2 TBSP olive oil on top of dough. Sprinkle about half the cheese, then arrange tomato slices on dough. Sprinkle with remaining cheese.
Bake at 375 for 30-35 minutes, until the cheese on top of the flatbread is beginning to brown. Let cool and slice to serve. Top with thin slices of fresh basil if you'd like. (I adore fresh basil, so I take every opportunity to use it!)