Begin heating the oil in a pot. Add the onions and cilantro. Cook down for 5 minutes or so. Add in all the tomatoes and cook down on medium heat for 25 - 30 minutes.
Place the tilapia on a baking tray. Top with the adobo seasoning. Then, top with as much salsa as you can fit on the fillet. Bake in a 325 degree oven for 6 - 8 minutes.
Serve and enjoy!