Tiny Tarts: How To Make Pie In A Jar Pie In A Jar Is Just That — It’s A Small Single Serving Of Fruit Pie Made And Baked In A Tiny Mason Jar. These Pies Are Frugal To Make, Awesome To Gift, Tasty To Serve, And Fun To Sell At Bake Sales Where There’s More Than Enough Standard Cakes And Tarts To Go Around.