Saute onions in olive oil till translucent, add black beans, salt and pepper. Stir till mixed. Add cumin. Mix and let warm through. Then, take about half the mixture and mash with a fork to just smooth out some of the beans. Add to remaining whole beans and mix together. Set aside.
Warm olive oil in sauté pan adding corn, red peppers and red onions. Cook just till corn softens about 3 -4 minutes. Remove from heat and put into bowl. Add lime juice, jalapeno, and fresh cilantro. Mix gently.
Warm corn tortillas in pan used to saute corn mixture. Flavors will infuse into tortillas.
Fill tortillas first with black beans, then add corn mixture. Top with cheese and avocado. Feel free to be creative and add tomatoes or salsa if desired.