Preheat oven to 350 degrees F. Spray 2- 8" cake pans with cooking spray; set aside.
In a medium bowl, whisk together flour, chai spice, baking powder, baking soda, and salt. Set aside
In a large bowl, combine melted butter and sugar. Mix together on medium speed for 2 minutes until thickened. Add eggs one at a time, mixing until blended between each one. Add vanilla and blend well.
Add the buttermilk and flour mixture in alternate additions, beginning and ending with flour. Mix until just combined - don't overmix.
Divide batter into cake pans and bake 15-20 minutes. When done, allow to cool in pan 5 minutes before removing to cooling rack.
Assembly
When the cake is cooled, pull ice cream out of the freezer and allow it to warm up for 5-10 minutes, until it's malleable. Spray the inside of a 3-quart bowl with cooking spray, then line with plastic wrap, pressing it flush against the interior of the bowl.
Using a 6-inch plate, cut a round out of one layer of the cake and press it into the bottom of the bowl. Transfer the entire half gallon of ice cream into the bowl and press down, evening out the surface. Place the second 8-inch cake layer on top.
Place the plastic wrap over it and freeze for at least 4 and up to 24 hours.
Meringue
When ready to serve, make the meringue. Whip the egg whites and cream of tartar in a large bowl with a mixer on medium-high speed until foamy, about 2 minutes. Gradually beat in the sugar on high speed until the whites are glossy and hold stiff peaks.
Remove the top layer of plastic wrap, then invert the cake onto a parchment-lined baking sheet or cake plate (if using torch to brown.) Remove the plastic wrap and cover the ice cream completely with the meringue, making sure to "seal" the bottom of the cake plate with the meringue. Form swirls and peaks in the meringue using the back of a spoon.
Using a kitchen torch, toast the outer layer of meringue to desired brownness. OR preheat the oven to 500 degrees and bake the cake until the meringue peaks are golden, 4-5 minutes. Let the cake soften at room temperature for 5 to 10 minutes before slicing. Enjoy!