In a large pot over medium-high heat, add olive oil.
Add in yellow onion and saute until translucent (about 3-4 mins).
Put garlic cloves and cook for 1 more minute.
Add in bell pepper and cook for another minute.
Top with diced tomatoes, vegetable stock, quinoa, black beans and corn.
Add in spices and bring soup to a boil.
Once boiling, cover with lid and simmer for 20 minutes.
Remove lid and simmer for an additional 20 minutes.
Top with lime juice, cilantro and cayenne if using.
Add to bowls and sprinkle with toppings of choice.