Heat the extra virgin olive oil in a large pot or Dutch oven over medium heat. Add the onion, garlic, carrots, and red bell pepper. Cook for 6–8 minutes, stirring occasionally, until the vegetables begin to soften.
Add the mushrooms and cook for 3–4 minutes, until they release their moisture. Stir in the tomato paste and cook for 1 minute, allowing it to caramelize slightly.
Add the spinach, cumin, chili powder, smoked paprika, oregano, and cayenne pepper (if using). Stir until the spinach has wilted.
Add both cans of black beans, including all of the liquid, along with the fire-roasted diced tomatoes. Stir well to combine.
Bring the stew to a gentle boil, then reduce the heat to low. Simmer uncovered for about 30 minutes, stirring occasionally, until the vegetables are tender and the stew has thickened.
Stir in the red wine vinegar or fresh lime juice just before serving. Taste and season with salt and freshly ground black pepper, if needed.
Serve warm on its own or over brown rice or quinoa. Garnish with fresh cilantro, diced avocado, crumbled feta cheese, or pumpkin seeds, if desired.
