Farmer's markets usually want to include a variety of vendors who sell diverse products so not only vegetables or not only jams or jellies. First step would be to double check with the market to make sure they have space for your type of product in case there are already multiple vendors selling baked goods. 

Next you want to see how your items can be sold. Cakes can fall under the Cottage Food Law if they can safely be kept at room temperature and do not require refrigeration so meeting the requirements for cottage foods. Further guidelines for selling cottage food items can be found here: https://www.michigan.gov/mdard/food-dairy/michigan-cottage-foods-information. 

For guidance on specific items, it would be best to follow up with your local MDARD Food Inspector:
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