Please quote the section of the Constitution that authorizes the government to deny freedoms based on commercial activities.
The Commerce Clause, empowering the Congress to set rules for the orderly and fair conduct of commerce. You can't claim "religious freedom" to cheat your customers, or to discriminate against them because of their race, etc. The community (by its elected representatives) is perfectly able to constrict your "freedom" with respect to commercial activities.
If you advertise the cake, and your customer asks for what you advertise to provide, then just bake it and can the religious crap.