Preheat the oven to 200 °C / 390 °F. In a blender or stand mixer, crush the pretzels into fine crumbs. Transfer to a large bowl, and add sugar and melted butter. Stir to combine. Transfer to an 8-inch springform pan. Press evenly into the bottom of the pan, then transfer to the preheated oven to bake. Bake for 8 - 10 minutes at 200 °C / 390 °F or until golden brown and baked. Set aside to cool to room temperature.TipIf you aren't using a springform pan, make sure to line the pan with baking paper to prevent the crust from sticking to the pan.
Cream Cheese Filling
Add mascarpone and cream cheese to a large bowl. Mix well using an electric mixer until creamy and combined. Add the lemon zest, lemon juice, vanilla paste, and sugar, and incorporate, then add the eggs and mix again until combined. Don't overwork the mixture. It should be creamy and combined but not fluffy.TipFeel free to use a stand mixer fitted with a whisk for this step.
Pour the cream cheese filling into the prebaked pretzel crust. Transfer the pan to a baking sheet and place it in the preheated oven on the middle rack. Bake for 60 - 70 minutes at 150 °C / 300 °F or at 135 °C (fan) / 275 °F (fan). The cheesecake is baked when the edges are set, but the center moves slightly when the pan is gently shaken. Take from the oven and bring to room temperature, then transfer to the fridge to cool for at least 3 - 4 hours, or overnight.
Strawberry jam topping
Cut half of the strawberries into small pieces. Add them to a saucepan along with the sugar, lemon juice, water, lemon zest, vanilla paste, and cornstarch. Place over medium heat and bring to a bowl, then simmer for 8 - 10 minutes or until the strawberries are soft and the sauce thickens. Cut the rest of the strawberries in half and add them to the saucepan. Cook for a minute, then remove from the heat and bring to room temperature. Transfer to a fridge for 1 - 2 hours or overnight.
Take the cheesecake from the fridge 10 minutes before serving. Cut into eight equal parts and serve with strawberry jam topping.