Step 1: Marinate the Chicken

1. In a large bowl, combine the Greek yogurt, lemon juice, ground cumin, ground coriander, garam masala, turmeric powder, chili powder, and a pinch of salt.
2. Add the chicken pieces to the marinade, making sure they are well-coated. Cover the bowl and refrigerate for at least 2 hours, preferably overnight, to allow the flavors to infuse.

Step 2: Prepare the Garlic Naan Dough

1. In a large mixing bowl, combine the all-purpose flour, salt, sugar, and baking powder.
2. Add the yogurt, warm water, and vegetable oil. Mix well until a soft dough forms.
3. Knead the dough for about 5 minutes on a lightly floured surface until smooth.
4. Cover the dough with a damp cloth and let it rest for 1 hour.

Step 3: Cook the Butter Chicken

1. In a large skillet or heavy-bottomed pan, heat 1 tablespoon of vegetable oil and 1 tablespoon of butter over medium heat.
2. Add the chopped onion and sauté for 5 minutes, until soft and golden.
3. Stir in the minced garlic and grated ginger. Cook for another 2 minutes until fragrant.
4. Add the marinated chicken pieces and cook for 5-7 minutes until browned on all sides.
5. Pour in the tomato puree and ground fenugreek (if using). Simmer for 10-15 minutes until the chicken is cooked through and the sauce thickens.
6. Stir in the heavy cream and remaining tablespoon of butter. Cook for an additional 5 minutes. Season with salt to taste.
7. Remove from heat and garnish with chopped cilantro.

Step 4: Cook the Garlic Naan

1. After the dough has rested, divide it into 6 equal portions and roll each into a ball.
2. Flatten each ball into an oval or round shape about 1/4-inch thick using a rolling pin.
3. Heat a skillet or cast-iron pan over medium-high heat. Cook each naan for 1-2 minutes on each side until bubbles form and brown spots appear.
4. In a small bowl, combine the melted butter with minced garlic. Brush the hot naan with garlic butter and sprinkle with fresh cilantro.

Step 5: Prepare the Creamy Tomato Yogurt Sauce

1. In a medium-sized bowl, combine the Greek yogurt, tomato puree, lemon juice, ground cumin, and cayenne pepper.
2. Season with salt and pepper, to taste. Mix well until smooth.
3. Garnish with fresh cilantro. Serve chilled or at room temperature as a dressing for the Butter Chicken or a dip for the Garlic Naan.