Start by lightly spraying an 8×8-inch baking pan with nonstick spray. This ensures that your cheesecake will slide out easily when it's time to serve.
In a medium-sized mixing bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Mix them thoroughly until the crumbs are well-coated in the butter.
Press the crust mixture firmly into the bottom of the prepared baking pan, making sure it’s evenly distributed. This step is crucial for a solid base that won’t crumble when you slice into the cheesecake.
Next, using a stand mixer or a medium-sized mixing bowl with a handheld mixer on medium-high speed, beat the softened cream cheese and vanilla together for about 1 to 1½ minutes. The mixture should be smooth and creamy.
Add in the cool whip and continue to mix just until combined. Be careful not to over-mix; you want to keep the light, fluffy texture.
Gradually add the powdered sugar, mixing until it’s completely incorporated. This will sweeten the filling without making it too heavy.
Evenly spread the cheesecake filling on top of the crust, using a spatula to smooth it out. Cover the cheesecake with plastic wrap and chill it in the refrigerator for at least 4 hours, or overnight if possible. This helps the flavors meld together.
While the cheesecake chills, prepare the fruit topping. In a heavy-bottomed 3 to 4 quart saucepan over medium heat, combine the strawberries, rhubarb, lemon zest, lemon juice, vanilla, granulated sugar, and cornstarch. Stir to combine completely, ensuring the fruit is well-coated.
Cook the fruit mixture on medium heat for 8 to 10 minutes, stirring continuously until the rhubarb softens and the topping thickens. You want a glossy, thick texture that will hold up when spread over the cheesecake.
Once cooked, allow the topping to cool completely before spreading it over the chilled cheesecake. This step prevents the heat from affecting the cheesecake's texture.
Finally, evenly spread the cooled fruit topping over the cheesecake. Cover again and chill for an additional hour before serving, if possible, to let the flavors meld.
