Prepare the Pan: Preheat your oven to 160°C (320°F) for a conventional oven, or 140°C (295°F) if using a fan-forced oven. Take a 20 cm (8-inch) springform pan and flip the base upside down. Lightly grease the bottom and line it with parchment paper that extends beyond the edges for easy removal. Grease the sides of the pan as well.
Make the Biscuit Crust: Place the biscuits in a food processor and pulse until they become fine crumbs. Add the melted butter and pulse briefly until the mixture resembles damp sand. Press the crumbs evenly into the prepared pan, pressing firmly against the bottom and up the sides to form a sturdy crust. Use a flat-bottomed cup or measuring cup for even pressure.
Prepare the Cheesecake Filling: In a mixing bowl, beat the cream cheese on medium speed just until smooth—avoid whipping to prevent cracks. Add the flour and beat briefly to combine. Mix in the vanilla extract, sour cream, sugar, and lemon zest until incorporated. Add the eggs one at a time, mixing briefly after each, just until blended. Pour the filling over the biscuit crust, smoothing the surface gently.
Bake the Cheesecake: Place the springform pan in the oven and bake for about 55 minutes. The top should turn a light golden color without cracking, and the center should still slightly wobble when gently shaken. Once done, leave the oven door slightly ajar and let the cheesecake cool inside for 20 minutes to prevent surface cracking.
Chill the Cheesecake: Transfer the cheesecake to the refrigerator, keeping it in the pan, and chill for at least 4 hours or overnight to set completely.
Prepare the Strawberry Topping: In a saucepan, combine the diced strawberries, sugar, vanilla extract, and lemon juice (or water). Cook over medium heat, stirring occasionally, until the strawberries break down and release juices, about 10 minutes. Mix the cornstarch with water to form a slurry and stir it into the pan. Add the halved strawberries and cook for another minute until the sauce thickens to a syrupy consistency. Remove from heat and cool completely.
Assemble and Serve: Once the cheesecake is chilled and firm, carefully remove the sides of the springform pan. Use the parchment paper to slide the cheesecake onto a serving platter. Spoon the cooled strawberry sauce evenly over the top, arranging the halved strawberries cut-side down for a beautiful presentation. Chill for an additional 2 hours before slicing and serving.