Preheat the oven to 350°F and line a large baking sheet with parchment paper.
In a large bowl, whisk together the almond flour, psyllium husk powder, baking powder and salt until no lumps remain.
In a second bowl, whisk the eggs, sour cream, melted butter and warm water until smooth.
Pour the wet ingredients into the dry ingredients and stir until a thick batter forms. Let it rest for 5 minutes so the psyllium can absorb the liquid and the batter holds its shape.
Scoop the batter into 6 equal mounds on the baking sheet, spacing them well apart. With damp fingers, flatten each mound into a round about 4 inches wide and 1/2 inch thick, then sprinkle with the sesame seeds.
Bake for 20-22 minutes, until golden brown and firm to the touch.
Cool completely on a wire rack, then split each round in half horizontally. Toast the cut sides lightly before filling for the best sandwich texture.