I washed the Anaheim Peppers and dried them well.
I then put them on a skillet and roasted them until charred on all sides. As they were ready little by little I put them in a plastic bag for them to sweat and be able to take the skin off more easily -a long time ago I learnt this step was the most important one when roasting chiles as we do in Mexico. Afterwards, I took the skin off, opened them, and deseeded them.
Once the peppers well all clean and ready I placed them in a platter and filled them with some fresh slices of mozzarella.
Then I worked on a tomato sauce. For that, I added the tomato, onion and garlic in the blender and processed everything.
I added the olive oil to the saucepan and sautéd the sauce. I know it sounds strange, but do it. Then, add the tomato paste to kill the acidity and season to taste with salt and pepper. Let it then simmer for 10 minutes. You will see the color of the sauce change. This will indicate that the tomato is being cooked. Taste and rectify seasoning if needed.
When serving, I warmed up a bit the peppers for the cheese to met. This can be very easily achieved in the oven preheated at 350 °F or 180 °C. Just wait for the cheese to be melted. It should take about 10 minutes or so.
Once plated, I sauced the peppers individually. Evidently, freshly handmade corn tortillas were in order.