In processor combine flour, yolk, salt and tomato paste; blend until well combined. Blend in water a few tablespoons at a time until a mealy dough is formed.
Turn dough out and shape into 4" balls. Press dough into 1" thick disks; wrap tightly in plastic wrap. Let the dough sit 30 minutes before rolling or cutting.
Roll dough out or flatten with your hand. Set pasta machine to its widest setting and feed the dough through the machine. Reroll dough, narrowing the setting on the machine each time, until the sheet is very thin. Cut into desired shapes. Cover loosely and refrigerate until needed.