Prep the pan and oven. Heat the oven to 325°F (163°C). Line the bottom of a 9-inch springform pan with parchment and lightly spray the sides.
Wrap the outside of the pan with foil to protect against leaks if you plan a water bath.
Make the crust. In a bowl, combine almond flour, oats, coconut sugar, melted light butter, vanilla, and salt. Mix until it looks like slightly damp sand. Press firmly into the bottom of the pan.
Bake for 10 minutes, then cool while you make the filling.
Cook the raspberry swirl. Add raspberries, sweetener, and lemon juice to a small saucepan over medium heat. Cook 5–7 minutes, stirring and gently mashing, until juicy. Stir in the cornstarch slurry and simmer 1 minute until thickened.
Set aside to cool slightly, then press through a sieve if you want it seedless.
Beat the filling base. In a large bowl, beat softened cream cheese with sugar on medium speed until smooth and fluffy, about 2 minutes. Scrape the bowl.
Add the rest of the filling. Beat in Greek yogurt, vanilla, lemon zest, and lemon juice until smooth. Mix in cornstarch and salt.
Add eggs one at a time on low speed just until blended. Do not overmix—too much air can cause cracks.
Assemble. Pour two-thirds of the cheesecake batter over the crust. Spoon half the raspberry sauce in small dollops over the surface. Add the remaining batter, then dot with the remaining raspberry sauce.
Drag a skewer or knife through the top to create gentle swirls. Don’t over-swirl or the colors will muddy.
Bake with care. For extra insurance against cracks, place the pan in a larger roasting pan and pour in hot water to come halfway up the sides (a water bath). Bake 45–55 minutes, until the edges are set and the center wobbles slightly like gelatin.
Cool slowly. Turn off the oven, crack the door, and let the cheesecake rest inside for 45 minutes. Remove from the oven and water bath, then run a thin knife around the edge.
Cool to room temperature, then chill at least 4 hours, preferably overnight.
Finish and serve. Release the springform, transfer to a plate, and garnish with fresh raspberries or a light dollop of whipped topping. Slice with a warm knife for clean cuts.