Preheat & prepare pan: Preheat oven to 160°C / 325°F. Grease a 9-inch springform and line base with parchment.
Make crust: Combine almond flour, powdered allulose and salt. Stir in melted butter until the mixture holds when pressed. Press into the base (and up sides if desired). Blind-bake 8–10 minutes until set and lightly golden. Cool.
Make dulce: In a saucepan, combine 200 g heavy cream, 56 g butter, and 80 g allulose. Simmer gently, stirring, until thickened and caramel colored (12–18 minutes). Stir in vanilla and salt. Reserve 120–150 g for the swirl; cool.
Make filling: Beat room-temp cream cheese until smooth. Add 100 g allulose and mix. Add eggs gradually (150 g total), then fold in 120 g heavy cream, 120 g sour cream, vanilla, and salt. Mix until silky (avoid overbeating).
Assemble: Pour two-thirds of batter into crust. Dollop reserved dulce in spoonfuls, top with remaining batter. Create 1–2 gentle swirls.
Bake in water bath: Wrap springform in foil. Place in roasting pan and add hot water to come halfway up sides of pan. Bake 55–70 minutes until edges set and center slightly jiggly. Turn off oven and cool with door ajar 30–60 minutes.
Chill: Refrigerate at least 6 hours, preferably overnight. Thin extra dulce with warm cream if desired and drizzle before serving. Slice with a warm knife, wiping between cuts.