1. Preheat oven to 350°F.
2. For the shawarma, begin by heating the olive oil over medium heat. Add the yellow onion and sauté for 3-5 minutes. Add the garlic, cumin, turmeric, coriander, black pepper, allspice, cinnamon, clove, fenugreek, fennel seed, and ras el-hanout. Cook the oil mixture for about 3 more minutes until the spices are aromatic. Remove from the heat, transfer to stainless steel bowl and allow to cool.
3. Combine the cooled spice oil with the mashed potatoes and eggs. Stir to combine and set aside.
4. Slice the russet potatoes thin on a mandoline, about 1/4-inch thick. Place in a large bowl and season them with olive oil, oregano, chili flakes, sumac, salt and pepper. Allow the potatoes to marinate for about an hour.
5. Prepare a sheet pan with a wire rack. Slice two rounds of pineapple about 1 –1/2 inches thick. Lightly spray the wire rack with olive oil or coconut pan spray.
6. Place one slice of the pineapple down on the wire rack. Dip the marinated slices of potato into the mashed potato and egg mixture (this is the “glue” that will hold the shawarma together). Working in a circle, overlap the sliced of potato directly on the pineapple and continue to work your way up until you have a potato tower about a foot and a half tall. Be sure to dip each slice of potato into the egg and mashed potato mixture.
7. When the potato slices are used up, gently place the pineapple on top of the potato tower and carefully place the shawarma in a preheated oven.
8. Allow the shawarma to cook for about 1 hour and 15 minutes.
9. While the shawarma is cooking, prepare your pickled vegetables. The process is the same for both pickles. Heat the vinegar, add the sugar and salt along with the herb/spices. Bring the mixture to a boil until the sugar and salt dissolve. Add the vegetables to their respective liquids and remove from the heat. Allow them to pickle for 5-7 minutes and immediately add the ice. Allow them to cool completely, drain, and serve or hold for 5-7 days.
10. For the Tomato Salad, combine all the ingredients together in a bowl and allow to marinate for about 30 minutes before serving.
11. For the Mashed Potato Flatbread: Place the flour and potato mash onto your work surface. Using your hand start bringing the ingredients together until a sticky dough is formed. Roll this into a log and cut into 24 pieces (every 1 cup of flour and 1 cup of mashed potatoes will make approximately 8 flatbread). Form each piece into a round shape. Make sure the surface you are working on and dough is dusted with flour before you start rolling out the dough. Roll out dough until it is quite thin. Cook each disk on medium to high heat on a dry frying pan for about 2 minutes (1 minute per side) or until done. Best served right away while still warm.
12. For the Tzatziki: combine all the ingredients for the sauce in a bowl and keep cold until ready to use
13. To service, remove the shawarma from the oven, allow it to rest and cool for about 8-10 minutes. Slice the shawarma tableside and serve on the flatbread with the sauce and pickled vegetables. Serve the tomato salad on the side.