Butter isn’t totally off limits, just use less of it. Using reduced-fat sour cream to replace some of the butter found in traditional recipes keeps the dough moist and tender, without adding tons of saturated fat.
And be sure to follow the basic rule of great pastry: dough likes to be cold. If the butter melts into the flour, the crust will be tough. So always use chilled butter and ice-cold water, work the dough with a light hand, and let the dough chill before rolling it out.