
Char the vegetables. Place the tomatoes, onion, jalapeño pepper, and garlic on a sheet pan (I'm using a ¼ sheet pan). Place 4 to 6 inches under the broiler in the oven, and broil for about 3 to 4 minutes, until lightly charred on one side. Use tongs to flip everything over and continue broiling for another 3 to 4 minutes. This step builds that signature smoky flavor. Alternatively, you could char the vegetables on a comal.
Peel and blend. Remove the garlic from its skins. Add the tomatoes, onion, jalapeño pepper, and garlic to a blender. Blend until mostly smooth.
Simmer the sauce. Heat the oil in a skillet over medium heat. Pour in the sauce (be careful as it may splatter). Stir in the cumin, oregano, and salt. Simmer gently for about 5 minutes, to deepen the flavor. If desired, you can add a bit of water for a thinner sauce.
Finish and serve. Remove from the heat, and stir in fresh cilantro before serving.