Preheat the oven to 180°C (356°F).
Melt the butter using a double boiler or microwave.
In a bowl, whisk together eggs and low-sugar sweetener until well combined.
Add the melted butter and vanilla extract, mixing thoroughly.
Sift in almond flour, baking powder, unsweetened cocoa powder, and salt, then combine gently.
Fill the madeleine molds about 80% full with the batter.
Bake in the oven at 180°C (356°F) for 10–12 minutes until done.