The short answer
Try chebakia, honey-soaked sesame flowers; gazelle horns, almond paste in a thin pastry crescent; sellou, a toasted flour, sesame and almond mound; and sfenj, the fried Moroccan doughnut. Pastry shops on Souk Semmarine sell sweets by weight, and the medina has specialists for gazelle horns.
In more detail
Chebakia are strips of dough folded into a flower, fried, soaked in honey and rolled in sesame. They belong to Ramadan, when families fold hundreds and shops pile them in pyramids, and they are eaten with harira. Gazelle horns, kaab el ghazal, are a crescent of thin pastry around almond paste scented with flower water. In Darija the name means the gazelle's heel, though everyone outside Morocco calls them horns. They come with tea when guests arrive and at Eid and weddings.
Sellou, also called sfouf, is never baked: flour is toasted, then mixed with sesame and almonds into a dark, crumbly mound, eaten by the spoonful. Sfenj are rings of fried dough, sold fresh; Sfenj Boulabada in the medina specialises in them, and they are vegan by default.
Where to buy: Patisserie Belkabir and Duniya Patisserie sit side by side on Souk Semmarine, selling nut-filled sweets by weight. Chez Brahim on Rue Riad Zitoun el Jdid is known only for gazelle horns. Maison Sucrée in a Mouassine souk stall makes brightly coloured ones. In Gueliz, Amoud has made pastries since 1982.
If you are offered sweets with tea in a home, take one. Turning down both tea and sweets reads as cold.