For pastry, in a mixing bowl beat the butter and cream cheese until combined. Stir in the flour. Wrap in plastic wrap and chill in refrigerator for 1 hour, if desired.
Shape the dough into 24 balls; place in ungreased 1-1/2-inch muffin pans. Press dough evenly against bottom and up sides of each muffin cup.
For the filling, in a mixing bowl beat together the egg, brown sugar, vanilla, and salt just until smooth. Stir in cranberries and pecans. Spoon filling into the pastry-lined muffin cups.
Bake tassies in a 325 degree F oven for 30 to 35 minutes or until pastry is golden brown. Cool in pans on wire racks. Remove from pans by running a knife around the edges. Store in airtight container. Makes 24 tassies.