1 teaspoon olive oil
1 medium yellow onion, finely chopped
2 cloves garlic, minced
3 heaping cups finely chopped rhubarb (about 4 large stalks)
Juice of 1 large orange
2 tablespoons tomato paste
2 tablespoons pure maple syrup
2 tablespoons tamari, gluten-free soy sauce, or coconut aminos
2 teaspoons yellow mustard
1 teaspoon chili powder
1 (350g-ish) block tofu, cut into 12 slabs, pressed of excess moisture, seasoned with salt and pepper

Heat the oil over medium-high heat in a shallow saucepan with a lid. Add the onion and cook until it begins to soften, about 4 minutes. Add the garlic and continue to cook for an additional minute. Add the rhubarb, orange juice, tomato paste, maple syrup, tamari, yellow mustard, chili powder. Mix well, cover, and simmer, about 10 minutes, until rhubarb is softened. Use a handblender to puree until smooth, or transfer the mixture or a heat-safe blender or food processor and process until smooth. Taste for seasoning—depending on your brand of tamari, soy sauce, or coconut aminos, you may want to add a pinch of salt.

Put the tofu in a shallow baking dish and cover with the sauce (you may have some leftover). Marinate for at least 3 hours.

Preheat a grill to 400F. Generously oil the barbeque grate. Put the tofu on the grate and grill for about 5 to 7 minutes (flipping it too early will cause it to stick). Transfer it to a plate, re-oil the grate, and grill on the other side for an additional 5 to 7 minutes. Serve warm, either on its own or in a sandwich, with additional sauce if desired.