Melt the butter in a small skillet over medium heat. Add the tandoori masala and toast, stirring often, until fragrant, 2 to 3 minutes. Whisk the spice mixture into the yogurt in a large bowl. Then mix in the ginger, lemon juice, salt and garlic. Add the chicken and toss to coat well. Cover and chill for at least 1 hour, preferably 6 hours and no more than 8 hours.
Preheat the oven to 350 degrees F.
Arrange the chicken on a greased baking sheet and bake until cooked through and an instant-read thermometer inserted in the chicken measures 165 degrees F, 12 to 15 minutes. Increase the heat to broil and broil 3 minutes.
Add the chicken to the Tikka Masala Sauce. Toss to combine. Serve the chicken with the sauce.
Tikka Masala Sauce:
Melt the butter in a large saucepan over medium heat. Add the fenugreek leaves and tandoori masala and toast, stirring often, until fragrant, 2 to 3 minutes. Add the marinara sauce and bring to a simmer. Add the cream, honey and salt to taste and simmer until the oil and butter start to float on the surface, about 5 minutes.