Whisk together ingredients for sauce, and set aside.
Prepare zucchini by cutting in quarters, lengthwise, then slicing.
De-seed red bell pepper, then cut into bite-sized chunks.
Drain tofu, pat dry, and cut into cubes.
Heat 1 tablespoon vegetable oil in a large nonstick skillet or wok over medium-high heat, then add tofu. Sauté tofu until lightly browned, stirring occasionally, about 5-8 minutes. Remove from pan.
Add ½ tablespoon oil, then add sliced onions, garlic, and ginger to the pan. Sauté for three minutes, then add another ½ tablespoon oil.
Stir in zucchini and red pepper. Cook 10-12 min over high heat until zucchini and red pepper are tender and beginning to brown, stirring frequently. Depending on your stove and pan, you may need to turn the heat down to medium-high to make sure nothing burns. But keeping it at as high heat as possible will give you those nice browned edges that are so delicious.
Add tofu back into the pan and stir.
Give the sauce another quick whisk to make sure the cornstarch is well incorporated.
Make a well in the center of the pan, then pour in the sauce.
Stir quickly while sauce thickens and turns into a glaze, about 30 seconds, then serve.
Notes
Leftover Zucchini Stir-Fry will keep in the fridge in an airtight container for 3-4 days. You can also freeze in an airtight container for up to 3 months. Wait to package for the refrigerator or freezer until it has cooled completely. Ingredient Substitutions:
Soy Sauce: For a gluten-free recipe, make sure you use tamari rather than traditional soy sauce—just check the tamari sauce packaging to make sure it is entirely gluten-free.
Brown Sugar: Either light or dark brown sugar can be used. If you don’t have either, try replacing with honey.
Red Bell Pepper: Feel free to replace with green, yellow, or orange bell pepper. I chose red since I love its slightly sweet flavor and bold color, but other peppers would also work. You could also replace with a different vegetable entirely, such as mushrooms—just note that mushrooms have more water in them than bell peppers. Add the mushrooms early enough to release some moisture before you add the zucchini.
Red Onion: You can replace this with a yellow or white onion or a shallot. You could also chop up some scallions and use those instead—if so, add the garlic and ginger with the zucchini and red pepper, along with half of the scallions. Use the other half of the chopped scallions for garnish.
Tofu: You can replace this with lots of other kinds of proteins. Try replacing with shrimp or chicken, for example. Or leave it out entirely for an all-vegetable stir-fry.
Crushed Red Pepper: I like my stir-fries with a little bit of spice but not a ton. If you like less, leave it out. If you like more, add more! (Or do what my husband does and pour sriracha over the final dish.)