Prepare pan: Grease a 10-inch tart pan and place in the freezer.
Make dough: Mix flour, hazelnuts, baking powder, salt, cinnamon, and sugar. Add vegan butter and cold water, then knead into dough.
Divide dough: Split dough into two portions, wrap one, and chill. Roll out the other portion into the pan, pressing down evenly.
Spread jam: Layer your favorite red jam over the base of the dough.
Form lattice: Roll out the remaining dough, cut into strips, and form a lattice on top of the jam. Press edges to seal.
Brush & sprinkle: Brush with dairy-free cream (with turmeric for color), then sprinkle with slivered almonds.
Bake: Preheat the oven to 355°F (180°C) and bake for 25-30 minutes.
Cool: Let the tart cool completely before serving.