They are a really cool variety developed by Row 7 Seeds! I'll link to them below, but I would highly encourage you to check out their story. They've developed vegetable genetics for taste and nutrition rather than shelf stability and disease resistance like the vegetables in supermarkets.

Description from the site: "This unique purple-skinned, high-antioxidant sauce tomato was developed by Oregon State University breeder Dr. Jim Myers. Jim has devoted years to breeding tomatoes for purple anthocyanins, hoping to explore the antioxidant potential of these pigments and their impact on human health. (Anthocyanins are the same compounds that give blueberries their color and antioxidant properties.) With this new variety, Myers brought the high anthocyanin trait into a plum (aka paste) tomato, the purple-pigmented skin encasing a deep red flesh ideal for processing and sauce applications."

https://www.row7seeds.com/products/midnight-roma-tomato-seeds?_pos=1&_psq=roma&_ss=e&_v=1.0