Place Instant Pot to “sauté” mode. Add olive oil, carrots, celery, onions and garlic. Sauté for 5 minutes until instant pot reaches “hot”. While sautéing chop the bell pepper, tomatoes, and spinach. Add the bell peppers to the Instant Pot and keep the tomatoes and spinach to the side.
Add the lentils, chicken bouillon cubes, Italian seasoning, red pepper flakes, salt, black pepper, and water to the Instant Pot. Mix well, close lid, and place the valve to “sealing” mode. Turn the Instant Pot off and select “manual” mode. Set the IP for 12 minutes (it will take 10-12 minutes to come to pressure then the count down begins).
Once the soup is done cooking let rest for 5 minutes. Using a kitchen towel and insulated pot holder, carefully force the remaining pressure. Carefully, remove the lid, stir and stir in the chopped tomatoes and spinach. Ladle into bowls and drizzle with additional olive oil and sprinkle with grated Peccorino Romano cheese.