Beat the egg whites and salt with the whisk of the mixer until stiff (if possible, not too fast, use the small or medium setting of the hand mixer). Add the powdered sugar and lemon juice by tablespoon. Beat for 3 - 4 minutes. Then carefully fold in the almonds, pistachios and lemon zest with a spoon.
Pour the batter into a piping bag and squirt walnut-sized biscuits onto a baking sheet lined with baking paper. Stick 3 pistachios in the middle. Bake the macaroons in the preheated oven (top / bottom heat: 150 ° C, fan: 130 ° C, gas: level 1 - 2) for 12 - 15 minutes.
Melt the couverture in a water bath. Let the macaroons cool and remove them from the baking paper. Dip the underside of each macaroon into the couverture. Let dry on a wire rack.