Pat out dough on a work surface; sprinkle with minced onion and knead until combined. Divide dough in half. Shape each half into 5 balls. To form knots, roll each ball into a 10-in. rope; tie into a knot. Tuck ends under. Place rolls 2 in. apart on a greased baking sheet.
In a small skillet over medium heat, melt butter. Add garlic and salt; cook and stir 1-2 minutes. Brush over rolls. Cover and let rise until doubled, about 30 minutes.
Preheat oven to 375°. Brush tops with egg; if desired, sprinkle with poppy seeds. Bake until golden brown, 15-20 minutes.
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