Prep the pan and oven: Heat the oven to 325°F (163°C). Line an 8x8-inch baking pan with parchment, leaving overhang for easy lifting.
Lightly mist with oil.
Make the crust: In a bowl, stir almond flour, sweetener, and salt. Add melted butter and vanilla. Mix until it looks like damp sand and clumps when pressed.
Press and par-bake: Press the crust firmly and evenly into the pan.
Use the bottom of a measuring cup to compact it. Bake for 10–12 minutes, until lightly golden. Set aside to cool slightly.
Beat the cream cheese: In a mixing bowl, beat softened cream cheese on medium speed until smooth and fluffy, about 1–2 minutes.
Scrape the bowl.
Add yogurt and sweetener: Beat in Greek yogurt and the sweetener until fully combined and silky. Scrape the bowl again.
Flavor and eggs: Mix in vanilla, lemon juice, zest, and a pinch of salt. Beat in eggs one at a time on low speed, just until incorporated.
Don’t overmix.
Pour and smooth: Spread the filling over the warm crust. Smooth the top with a spatula to even out the surface.
Bake gently: Bake at 325°F (163°C) for 22–28 minutes. The edges should look set, and the center should have a slight jiggle, not a slosh.
Cool and chill: Cool in the pan on a rack for 1 hour.
Then refrigerate at least 4 hours, preferably overnight, until fully set.
Slice cleanly: Lift out with the parchment. Use a sharp knife, wiping between cuts, to slice into 12–16 bars.
Top and serve: Add fresh berries, a sugar-free compote, or a dollop of whipped cream if you like. Serve chilled.