Which ingredient is commonly associated with tree nut allergies in baked goods?

Marzipan is a sweet almond paste made from ground almonds and sugar, making it directly related to tree nut allergies. Because it contains almonds, individuals with tree nut allergies must avoid marzipan to prevent allergic reactions. In baked goods, marzipan is often used for decorations or as a filling, reinforcing its association with tree nuts.

The other options do not pose the same risk. Rice flour is typically safe for those with nut allergies as it is derived from rice, a grain. Cornstarch is a carbohydrate derived from corn and does not have any association with nuts. Poppy seeds, while they might be included in baked goods, are derived from the opium poppy plant and do not relate to tree nuts. Therefore, marzipan stands out as the ingredient that poses a direct risk for individuals with tree nut allergies in baked products.