Add frozen corn, chopped sweet bell pepper, jalapeno pepper (if using) and ½ cup of water, stirring to combine.
Add rinsed and drained beans, quinoa, canned tomatoes, generous ½ cup salsa, remaining salt and 1 cup of water, stirring to combine.
Bring to a gentle boil and then lower to simmer and cover with lid.
Allow quinoa to cook for about 20 minutes, stirring now and then, until the quinoa has softened and expanded (most of the liquid will have absorbed).
Taste and make any flavor adjustments, heat, salt, etc.
I like to mix in the remaining salsa and sometimes add more for service. Top as desired with guacamole or simply chopped avo; sliced and seeded kalamata olives; yogurt/cheese (plant-based as desired); chopped cilantro; lime wedges, etc.
Recipe by Inspired Edibles at https://www.inspirededibles.ca/2020/04/black-bean-mexican-skillet.html