Wash your hands with soap and water. Use a child-friendly knife and cutting board to cut the tomatoes into quarters. Place them in a clean bowl and set aside.
Cut the green bell pepper and onion into quarters as well. Place them in a clean prep bowl.
Chop the cilantro and culantro. Place in a clean bowl and set aside. This is also a great time to smash those garlic cloves if you have them. If you're using already minced garlic like we did here, you can move on to the next step.
Transfer the tomatoes to the blender and turn the blender on. Blend until they are finely chopped and then stop. Do the same with the onion and garlic. Finally, repeat for the bell pepper, culantro, and cilantro.
Process until the sofrito is mostly smooth as seen above. You can use or serve immediately.
Notes
Wash produce under running water
Use a vegetable brush to scrub firm produce
Cover and store in the fridge for up to 1 day
Pour into an ice-cube tray to freeze for up to 6 months