Melt the butter in a pot without letting it get too hot. Somewhere between 60-70°C should be sufficient.

Place the egg yolks in a small bowl, add the salt, pepper, vinegar, and lemon juice. Blend with a hand blender.

Holding the blender in one hand and the pot with the melted butter in the other, keep blending and pour in the melted butter.

Remove the blender and season the sauce to taste with salt, pepper and lemon juice.