Peel and finely dice the onion and garlic. Heat 1 tablespoon of oil in a frying pan and sauté the onion and garlic. Add the spinach and 7 tablespoons of water and simmer at low heat for about 15 minutes.
Meanwhile wash the pork tenderloin, dab dry and cut into 8 slices. Heat 1 tablespoon of oil in a frying pan and fry the meat over high heat for 4-5 minutes. Remove and season with salt and pepper.
Stir the crème fraîche into the spinach, season with salt, pepper and nutmeg. Cut baguette into 8 slices and place on a baking tray. Spread the spinach, meat and cheese on top and slide under the preheated grill of the oven and cook for 2-3 minutes until golden brown.
Remove and serve immediately.