Ponderosa lemon
The ponderosa lemon originated in roughly 1887, and is believed to come from a chance seedling grown in Hagerstown, Maryland. It was later named and introduced to the nursery trade in 1900. Though often referred to as a cross between the lemon and citron, a recent genomic analysis showed it to solely contain pomelo ("Citrus maxima") and citron ("Citrus medica") DNA, perhaps being an F2 hybrid. Thus they cannot derive from true lemons, which have a mandarin orange component.
Lemon tart
In the UK, lemon tart (also called tarte au citron) consists of a pastry case (often made in a fluted tart tin) containing a baked lemon custard (usually composed of eggs, sugar, lemon juice and cream). Usually recipes include blind-baking before adding the custard. Sometimes the tart is dusted with icing sugar prior to serving.