Add the lentils to a pan with plenty of water, and bring to a gentle boil. Cook until tender, around 30-35 minutes, stirring occasionally.

Meanwhile, heat a dash of oil in a large frying pan, and add the vegetables (onion through mushrooms). Cook over a medium heat, stirring regularly, for around 5-10 minutes, until they are soft and any excess liquid has been cooked off.

When the lentils are cooked, drain them and add to the cooked vegetables, along with the enchilada sauce. Mix well to combine. I also added about half of the grated cheese at this point, and stirred it through.

Transfer everything to a baking dish - mine measured around 8 x 8 inches. Top with the remaining grated cheese and some slices of tomato.

Bake for around 20 minutes, until the cheese has crisped up to your liking.