Whisk the peanut butter, garlic, ginger, soy sauce, vinegar, sriracha, sugar, and 2 tablespoons oil until combined. If the sauce is too thick, add hot water - 1 tablespoon at a time. (You can make the sauce while the cauliflower cooks.)
Preheat a large, non-stick sauté pan on medium-high heat. Add 1 tablespoon sesame oil and swirl to coat the pan. Add the cauliflower (in batches if needed). Cook 5 -7 minutes allowing the florets to brown slightly. Reduce heat to medium. Add red pepper slices. Cook just until tender, about 3 minutes.
Add peanut sauce (reserving a ¼ cup for extra dipping). Stir until heated through and the vegetables are well coated.
Remove pan from the heat. Sprinkle with chopped peanuts and optional garnishes. Serve warm.
Serve this cauliflower stir-fry with
Brown rice, quinoa, or chickpea pasta noodles for a filling protein boost. All of these keep the recipe vegan and gluten-free. But you can certainly add any side item you like or even eat it solo.