In a mixing bowl, combine the ginger, paprika, coriander, turmeric, cayenne, cumin, salt, pepper, garlic and lemon juice to make a paste. Drain the lamb of any excess juices, then add to the bowl with the spice mix and toss to coat fully, rubbing the spices into the meat.
In a large pot, heat 2 tablespoons of oil over high heat. Add the lamb and sear on all sides, working in batches to avoid crowding the pan. Place the seared lamb on a plate.
Heat another 2 tablespoons of oil in the pot over medium heat. Add the vindaloo paste, onion, garlic, ginger, crushed tomatoes, diced tomatoes, water, cilantro, salt, and pepper. Bring to a simmer, stirring. Turn off the heat and blend the sauce until smooth with an immersion blender.
Return the seared lamb to the sauce in the pot, along with the potatoes, and bring to a simmer over medium heat. Cook for 20-30 minutes, until the lamb and potatoes are cooked through and flavorful. Fold in the peas.
Meanwhile, place the rice, cardamom, garlic, 2 cups of water and a pinch of salt in a saucepan. Bring to a simmer, reduce to low, cover, and cook until the grains are tender, about 20 minutes.
Combine all of the mint yogurt ingredients in a small bowl. Whisk well and season to taste.
Divide the cardamom rice between bowls, top with lamb vindaloo and mint yogurt. Serve with naan on the side.