First, make the fruit jam. This step happens before anything else because the jam needs to cool completely before you swirl it into the cheesecake. If it's even slightly warm, it'll melt into the filling instead of creating those defined ribbons you're after.

Combine thawed and well-drained frozen rhubarb, sliced fresh strawberries, evaporated milk, sugar, and lemon juice in a small saucepan.

Cook over medium heat for 15 to 20 minutes, stirring often and using your spoon to mash the fruit as it softens.

When the mixture thickens into a glossy, spreadable jam, remove it from the heat and let it cool to room temperature.

The evaporated milk might seem random, but it gives the jam a creamier body that swirls better than a straight fruit reduction. Don't skip the draining step on the rhubarb or you'll end up with a watery mess that weeps into your cheesecake.

Next, bake the crust. This crust is unconventional but ridiculously effective. Mixing cake mix with heavy cream creates a soft, cookie-like dough that presses into the pan easily and bakes up tender but stable.

Preheat your oven to 350°F and line a 9x13-inch baking dish with parchment paper or grease it thoroughly.

Press the dough evenly into the bottom of the prepared pan using your hands or the bottom of a glass.

Bake for 10 to 12 minutes, just until the crust is slightly set but not browned.

The crust should look pale and barely firm when you pull it out. Overbaking it now means it'll turn hard and crumbly after the second bake. You want it just set enough to hold the cheesecake layer without soaking through.

Then, blend the filling and swirl. The filling comes together in minutes, but the order matters. Cream cheese needs to be completely smooth before you add anything else, or you'll end up with lumps that won't disappear no matter how long you mix.

In a large bowl, beat 4 blocks of softened cream cheese with a hand mixer until completely smooth and creamy.

Slowly pour in sweetened condensed milk, vanilla extract, and lemon juice. Mix until the filling is smooth and lump-free.

Pour the filling directly over your warm, baked crust.

Drop spoonfuls of the cooled fruit jam on top of the cream layer, then drag a butter knife gently through the jam and cream to create a marbled pattern.

Finally, bake and chill. Cheesecake bars need gentle heat and a slow cool-down to avoid cracks and maintain that silky texture.

Bake at 350°F for 35 to 40 minutes. The edges should be slightly puffed, and the center should have just a tiny wobble when you gently shake the pan.

Turn off the oven, crack the door open, and let the pan cool inside for 20 minutes. Remove the pan from the oven and let it cool completely on the countertop.

Refrigerate for at least 6 hours, or preferably overnight.

The slow oven cool-down prevents the sudden temperature change that causes cracks. The long chill time isn't optional. Cheesecake needs that cold-set period to firm up into sliceable bars. Cut them while they're still cold for the cleanest edges.