Wash and dry all produce. Bring 3/4 cup water and a pinch of salt to a boil in a small pot. Halve, peel, and finely dice onion. Set aside 2 TBSP diced onion in a medium bowl. Zest lime until you have 1/2 tsp zest, then cut into halves. Finely chop cilantro. Dice tomato. Finely chop lettuce.

Once water is boiling, add rice to pot. Cover, lower heat, and reduce to a simmer. Cook until tender, 15-20 minutes.

Heat a large drizzle of olive oil in a large pan over medium-high heat. Add onion and cook, tossing, until softened, 3-4 minutes. Add seitan and cook, tossing occasionally, until lightly browned and warmed through, 3-4 minutes. Reduce heat to low and keep on stove until ready to serve.

Halve, pit, and scoop flesh from avocado, then roughly chop. Add to bowl with reserved onion. Squeeze in juice from one lime half. Season with salt and pepper. Mash with a fork until mostly smooth. Stir in half the cilantro and just enough tomato to give guacamole a chunky texture. TIP: Toss any extra tomato into pan with seitan.

Once rice is done, fluff with a fork. Add lime zest and a squeeze of lime juice and stir to combine. Season with salt, pepper, and more lime juice (to taste).

Toss lettuce with a drizzle of olive oil in another medium bowl. Season with salt and pepper. Divide rice between bowls, then top with seitan mixture, lettuce, and guacamole. Sprinkle with Monterey Jack cheese, remaining cilantro, and any remaining lime juice (to taste).