Place beet in a small saucepan and cover with cold water. Bring to a boil over medium heat. Reduce heat and simmer until tender. Drain and let cool. Once cool, remove peel with your fingers.

Place beet in the bowl of a food processor, add about 1/4 cup water, and process until smooth, about a minute.

Meanwhile, in a medium bowl, mix together flour and salt. Make a well in the center and add the beet purée. Use your fingers to work into a dough. Turn out onto a clean work surface and knead until you have a smooth, non-sticky but supple, dough, about 5 minutes. As you work, you might have to add additional water or flour, depending on the size of your beet.

Wrap in plastic and let rest for 30 minutes before shaping.