Combine the blueberries with honey, a pinch of salt, Meyer lemon zest, and juice in a medium saucepot. Bring to a boil over medium heat and continue to simmer until the berries are softened, about 5 minutes. Let cool completely.
Brush a 3-quart bowl with oil and line it with plastic wrap.
Beat 2 cups heavy cream with a whisk until stiff peaks form. Add the condensed milk and beat for another minute. Fold in the roasted blueberries into the cream mixture. Transfer the ice cream to the prepared bowl and spread it in an even layer. Cover the ice cream with plastic wrap and chill until solid, about 5 hours or overnight.
Preheat oven to 350 degrees F. Spray 9-inch cake pan with cooking spray and line the bottom with parchment paper.
Combine flour, sugar, salt, baking soda, and baking powder in a large bowl. In a separate bowl, whisk together olive oil, buttermilk, eggs, lemon zest, and lemon juice. Add the wet ingredients to the dry, stirring just until combined. Pour the batter into the prepared cake pan and bake for 45 minutes - 1 hour or until a toothpick inserted comes out clean. Remove from oven and let cool on the wire rack.
Remove the plastic cover and place the cake on top of the frozen ice cream, gently pressing down on the cake. Trim the ends of the cake as needed. Cover with plastic and freeze until firm, about 2 hours or overnight.
Make the meringue. Whip the egg whites with the cream of tartar until they start to get foamy. Slowly add the sugar while the mixer is on and continue to beat the egg whites until stiff peaks form.
Remove the plastic cover on the ice cream and cake. Place a plate on the bowl and flip it upside down, transferring the cake onto the plate. Remove the plastic wrap and cover the cake with the meringue.
Freeze the cake for 3 hours or until solid. Remove from the freezer and use a blowtorch to torch the meringue. Cut into slices and serve.