Prep the oven and pans: Heat the oven to 350°F (175°C). Grease a standard donut pan or a muffin pan if you’ll punch holes later. You can also bake as rounds in a muffin pan and fill them like jelly donuts.
Mix the dry ingredients: In a large bowl, whisk almond flour, coconut flour, sweetener, baking powder, baking soda, salt, and cinnamon.
Break up any clumps for a smooth batter.
Combine the wet ingredients: In a separate bowl, whisk eggs, almond milk, melted butter, vanilla, and vinegar until smooth.
Make the batter: Pour the wet mixture into the dry. Stir until just combined. The batter should be thick but scoopable.
If it’s too thick, add 1–2 tablespoons almond milk.
Fill the pan: Spoon the batter into the donut pan, filling each cavity about 3/4 full. Smooth the tops. If using a muffin pan, fill each well about 2/3 full.
Bake: Bake 15–18 minutes, or until the donuts are set, lightly golden, and a toothpick comes out clean.
Muffin-style rounds may need 18–20 minutes.
Cool completely: Let donuts rest in the pan 5 minutes, then transfer to a rack. Cool fully before filling to keep the cream from melting.
Make the strawberry reduction: In a small saucepan, combine strawberries, 1 tablespoon powdered sweetener, and lemon juice. Cook over medium heat 5–7 minutes, stirring and mashing until thick and jammy.
Cool to room temperature.
Whip the cream: In a chilled bowl, whip heavy cream with the remaining 1 tablespoon powdered sweetener to soft peaks. Set aside.
Finish the filling: Beat softened cream cheese with vanilla and a pinch of salt until smooth. Fold in the cooled strawberry reduction, then gently fold in the whipped cream until light and fluffy.
Fill the donuts: Transfer filling to a piping bag fitted with a round tip (or a zip-top bag with the corner snipped).
Use a small knife or skewer to create a tunnel in each donut. Pipe the strawberry cream until you feel resistance and a little peeks out.
Finish with “sugar” dusting: Lightly dust with powdered sweetener. Serve chilled or at cool room temp for the best texture.