Lemon Ice Cream Base:
Combine whole milk, heavy cream, inverted sugar, egg yolks, granulated sugar, milk powder, and stabilizer in a large stainless steel bowl. Place the bowl over boiling water.
Stirring constantly, slowly cook the mixture until a thicker consistency. Add chopped candied lemon zest and lemon oil extract to the mixture. Cool down the mixture over an ice water bath. Cover and refrigerate the ice cream bath overnight. The next day, process in an ice cream maker according to manufacturer's directions.
Preheat the oven to 350 degrees F.
In the bowl of a stand mixer, cream the butter and sugar on low speed. Add flour, almond flour, and salt and continue mixing on low until fully incorporated, about 3 to 4 minutes. Using your hands, break the dough into small crumbles and place them on a baking sheet. Bake for 8 to 10 minutes or until golden brown. Let cool completely and cover with plastic wrap to keep dry.
Preheat the oven to 250 degrees F.
In a clean, dry mixing bowl, whip the egg whites to soft peaks. On low speed, gradually add the granulated sugar to the meringue, increase the speed, and whip the meringue to stiff peaks. Transfer meringue to a piping bag and pipe out the meringue into long cylinder shapes on a silpat or piece of parchment paper. Dust the tops with the powdered sugar. Bake for 2 hours. Let cool completely. Crumble the meringue and cover with plastic wrap to keep dry.
Lemon Tart Ice Cream:
Combine eggs, granulated sugar, powdered glucose, and fresh lemon juice in a large stainless steel bowl. Place the bowl over a large pan of boiling water. Stirring constantly, slowly cook the mixture to curd consistency. Place the mixture over an ice water bath and cool down to 100 degrees F. Add butter and combine well. Refrigerate the mixture until very cold.
Process the ice cream in an ice cream maker according to manufacturer's directions. Transfer the ice cream to a large mixing bowl and fold in the crumbles and meringue pieces. Then add the lemon ice cream base and fold to combine until the 2 ice creams are nicely marbled. Transfer to airtight containers and freeze until hardened, about 2 hours.