1. In a large frying pan, heat olive oil and add onion, garlic, and fresh herbs. Season with one and a half teaspoons and one teaspoon pepper and sauté until onions are translucent.
2. Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius), with the rack set in the center of the oven.
3. Put one slice of beef fry in a 10-inch (26-centimeter) cast-iron skillet, placing it so that one end starts in the center of the skillet and extends along the bottom
and up the side, allowing the other end to hang over skillet edge. Repeat the process using remaining beef fry slices, working in a circular pattern and overlapping slices slightly to completely cover the bottom and sides of the skillet. Once all the beef fry is in the skillet, use the palm of your hand to flatten the center to make sure there are no gaps in the meat. Sprinkle a little pepper on the bottom.
4. Combine remaining one and a half teaspoons salt and one teaspoon pepper. Starting around the edge of the skillet and working in toward the center, arrange potato slices in concentric circles, overlapping slices by about 1/3 inch (one centimeter), until the bottom of the skillet is covered. After finishing the layer, season potatoes with the salt and pepper mixture, and a quarter of the onion mixture. Repeat layering, following the same steps, until all potatoes have been used. Firmly press down the layers of potatoes so they’re even.
5. Fold overhanging beef fry neatly up and over the top of the layered potato mixture, working in a circular pattern and ensuring there are no gaps.
6. Cover the center of the skillet with five-inch (13-centimeter) round pieces of parchment paper and aluminum foil. Place skillet on a rimmed baking sheet.
7. Bake tart until beef fry starts browning around the edges, about one and a half hours. Remove aluminum foil and parchment and continue baking for about another hour, until a toothpick can be inserted easily. If the beef fry darkens too much, tent the skillet with aluminum foil.
8. Remove tart from oven and carefully pour off any excess liquid. Let it rest for 10 minutes or overnight. Use a spatula to loosen bottom and sides of tart, then invert onto a serving plate and slice into wedges.