Line a baking sheet with aluminum foil and place tomatoes on top. Set the oven rack directly underneath the broiler and turn the broiler on high.
Broil the tomatoes for 3-4 minutes, or until the skin is blackened and blistered. Carefully flip over the tomatoes and broil for another 3-4 minutes, or until the skin is blackened and blistered on all sides. Remove from the oven and set aside.
Preheat the oven to 450°F.
Add ground pork, breadcrumbs, egg, onion, garlic, salt, cumin, and coriander to a large mixing bowl. Gently combine using your hands until everything is just mixed. Be careful not to overmix or they may come out tough.
Shape the mixture into 16 meatballs and set aside.
Heat olive oil in a large cast-iron skillet (or other oven-safe skillet) over medium-high heat. Add meatballs to the skillet and sear until golden brown on one side, about 1-2 minutes.
Flip the meatballs over and transfer the skillet to the oven. Bake for 8 minutes, or until the internal temperature of the meatballs reach 160F.
While meatballs are baking, add the roasted tomatoes, garlic, chipotle peppers, adobo sauce, oregano and salt to a large blender. Blend until smooth, or pulse a few times if you prefer a chunky sauce.
Remove the skillet from the oven and pour the chipotle tomato sauce on top. Be careful of any splatters since the skillet will be very hot!
Stir the sauce in the skillet and let it sit and cook with the residual heat for 2 minutes. Garnish meatballs with chopped cilantro and serve.
Notes
Storage: The meatballs can be stored in the refrigerator in an airtight container for up to 4 days.
Freezing: To freeze any leftovers, simply place the meatballs along with all the sauce in a freezer-safe container or zip-top bag and freeze for up to 3 months.
To save some time, you can use 1 (28-ounce) can of fire-roasted tomatoes instead of roasting your own under the broiler. Just skip the roasting step and blend the canned roasted tomatoes with the rest of the sauce ingredients.
Don't overmix the meat mixture. Make sure to mix the ground meat mixture until it just comes together. Overmixing can cause the meatballs to be tough, which is no bueno!
Use a cast-iron skillet if you have one. I love using a cast-iron skillet for this recipe because it retains heat really well. When you take out the meatballs and pour the sauce on top, the heat of the skillet will continue to cook the sauce a bit and give it some extra depth of flavor.