Wash the tenderloin and remove any membrane, if present. Cut it lengthwise into slices about two fingers thick, or more precisely, into medallions. Season with salt, ground black pepper, and drizzle with olive oil. Let it rest for 10-15 minutes. If you suspect that you have bought older meat, it is worth leaving it to marinate overnight, which will make it slightly more tender.
Preheat the oven to 200°C (392°F), with the top and bottom heat and fan settings.
Peel the potatoes and cut them into finger-thick slices. Season with salt, drizzle with a little olive oil and set aside.
Pour a little olive oil into a heatproof dish and place the pork medallions in it. Grate two cloves of garlic over them. Pile the potato slices on top. Cover with aluminum foil and bake for 40 minutes.
After 40 minutes, add the zucchini, which you have also cut into finger-thick slices and salted. Cover with the zucchini and bake for about 10-15 minutes. Finally, remove the aluminum foil and bake until golden brown.
To serve, wash the Romaine lettuce thoroughly. Cut off the end, then cut it lengthwise into four pieces. Place on a serving dish and drizzle with the dressing.
Dressing: pour a carton of kefir into a mixing bowl. Add salt and crushed garlic. Mix well.