Heat a large skillet over high heat.
Crumble in tofu, and mash with a large spoon or potato masher to break it up into crumbles.
Cook for 5 minutes, or until browned and moisture evaporated.
While tofu is cooking, whisk together orange juice, soy sauce, rice vinegar, brown sugar, cornstarch, sesame oil, garlic powder, ground ginger, and orange zest if using in a bowl or liquid measuring cup.
When tofu is browned, stir in prepared sauce and water chestnuts. Cook an additional 5 minutes, or until sauce is thickened.
Serve in lettuce cups, and top with sesame seeds, chopped green onion, and sriracha if you want extra spice.
