In a large mixing bowl, combine 2 cups of the flour and the yest; set aside.
In a medium saucepan, heat and stir the milk, butter, granulated sugar, and salt just until warm (120-130 degrees F) and butter almost melts; add to flour mixture along with eggs.
Beat on low speed for 30 seconds, scraping the sides of the bowl. Beat on high speed for 3 minutes.
Stir in grapefruit zest, grapefruit juice, and as much of the remaining flour as you can.
Turn dough out onto a lightly floured surface. Knead in enough of the remaining flour to make a moderately soft dough that is smooth and elastic (3-5 minutes total). Shape dough into a ball.
Place in a lightly oiled bowl, turning to oil surface of dough. Cover; let rise in a warm place until double in size (about 1 hour).
Punch dough down. Turn out onto a lightly floured surface. Divide in half. Cover and let rest 10 minutes.
Lightly grease two large baking sheets, set aside.
Roll each dough half into a 12x7-inch rectangle. Cut each rectangle into twelve 7-inch long strips.
Tie each strip loosely in a knot. Place knots 2 inches apart on prepared baking sheets. Cover; let rise in a warm place until nearly double in size (about 30 minutes).
Preheat oven to 375 degrees F. Bake for 12-14 minutes or until golden.
Immediately remove from baking sheets. Cool on wire racks.
Drizzle with glaze.