In a small pot, combine rice, ¾ cup water (1½ cups for 4 servings), and a pinch of salt. Bring to a boil, then cover and reduce to a low simmer. Cook until rice is tender, 15-18 minutes.
While rice cooks, wash and dry produce. Thinly slice scallions, separating whites from greens. Core, deseed, and finely dice green pepper. Peel and mince or grate garlic. Quarter lime.
Heat a drizzle of oil in a medium pot (large pot for 4 servings) over medium-high heat. Add scallion whites and green pepper. Cook, stirring occasionally, until browned and softened, 5-7 minutes. Season with salt and pepper.
Stir in garlic, cumin, and Mexican Spice Blend; cook, stirring constantly, until fragrant, 30 seconds.
Stir in red lentils and their liquid, tomato paste, stock concentrate, ½ cup water, and ¼ cup sugar (1 cup water and ½ cup sugar for 4 servings). Bring to a simmer, then reduce heat to medium-low. Cook, stirring frequently, until flavors meld and chili has thickened slightly, 8-10 minutes.
Taste and season with salt and pepper.
Fluff rice with a fork.
Divide chili between bowls. Top with rice, sour cream, as much Mexican cheese blend as you like, and scallion greens. Serve with a squeeze of lime juice and remaining lime wedges on the side.
