1. Put the marzipan into a bowl of a food processor and start to blend it. Then add the whole eggs gradually and process until two ingredients become homogeneous.
2. When the whole eggs and the marzipan are combined, add the cornstarch. Lastly, pour in the grapeseed oil in a thin stream and process until smooth.
3. Pour the egg whites into the mixer bowl, add sugar and salt, and whip the meringue using a whisk attachment until fluffy, smooth and not too stiff.
4. Transfer the marzipan base to a clean bowl and immediately incorporate the meringue into it in two steps, folding it in gently using a spatula.
5. Add the chopped roasted pecans and incorporate them into the batter.
6. Fill the piping bag with the cupcake batter and pipe 40 grams of it into each paper cup. Fill no more than ¾ of the paper cup.
7. Bake the gluten-free cupcakes in the oven, preheated to 170 °C / 338 °F, for 10-12 minutes until they rise. When ready, the toothpick, inserted in the centre of the cupcake, should come out clean and dry.
8. Transfer the cupcakes on a wire rack and let them cool down at room temperature.