Is 'cupcake' a feminine or masculine word in French?

Cupcake is masculine in French. The French equivalent may be the English loan Word 'cupcake'. In this case, it's considered a masculine noun whose definite article is 'le'['the'], and whose indefinite article is 'un'. It's pronounced 'kuhp-kehk'.

Another equivalent is 'petit gâteau'. That's also masculine. The masculine adjective 'petit' means 'little, small'. The masculine noun 'gâteau' means 'cake'. Together, they're pronounced 'puh-tee gah-toh'.