Heat olive oil in a skillet over medium heat. Add onions and sauté until softened.
Add rice and 1-2 tablespoon of water as needed to the skillet and cook until warmed through, stirring frequently.
Stir in beans (including the reserved liquid) and salt, and continue to heat until warmed through.
Serve immediately with desired sides and toppings.
Notes
LeftoversStore leftovers in an airtight container in the refrigerator for up to 4 days or freeze for up to 3 months. Reheat with a splash of water in the microwave or on the stove.