Pour a small amount of neutral oil in the center of a 9-inch pie plate. Use a pastry brush to coat the plate in an even layer of oil, set aside.
Place the lentils in a small saucepan. Add the water and place over high heat. Once the water is boiling, add 1/2 teaspoon of the salt and cook the lentils until tender. This should take somewhere between 25-30 minutes. If you notice the lentils are cooking dry, add a little more water. Drain the lentils and set aside.
While the lentils are cooking, place the saffron in a mortar and pestle with a pinch of salt. Grind the saffron into a powder. Pour the hot water into the mortar and pestle and give it a quick swirl. Pour the mixture into a small bowl and set aside.
Preheat the oven to 400°F. Rinse the basmati rice until the water runs clear. Place a large pot of water over high heat. Once the water comes to a boil, add the remaining salt and the rice. Cook the rice until just shy of al dente, about 6-8 minutes. Drain the rice and return to the pot. Set aside to cool.
Pour the olive oil into a skillet. Heat over medium-low until shimmering. Add the garlic and saute until fragrant, about a minute. Add the preserved lemon and dried sour cherries and saute until softened, about 2 minutes more. Take half of the mixture out of the skillet and transfer to a bowl set aside.
Add the green lentils to the skillet along with the tuna. Saute until everything comes up to temperature. Stir in the honey and saute for another minute or two. Taste and season with additional salt accordingly. Take the skillet off of the heat and stir in half of the scallions. Set aside.
Spoon the yogurt into a large bowl. Add the egg yolks, oil and saffron water and whisk to combine. Fold in the rice and stir until each grain is completely coated.
Press half of the rice mixture into the base of the prepared pie plate. Spoon the lentil mixture on top and press into an even layer. Cover with the remaining rice and smooth the top. It will look like there is too much going into the pie plate. Just cover the surface with parchment or wax paper and press down.
Cover the pie plate with tin foil and place in the oven. Bake for 75 minutes or until the rice is set and the bottom is golden. Let cool in the plate for 10 minutes before inverting onto a large plate. Decorate the top of your tahchin with the reserved garlic, preserved lemons, and cherries. And sprinkle with the remaining scallions and mint leaves. Serve immediately.