1 can (12 ounces) frozen lemonade concentrate, thawed
1 tablespoon butter
2 teaspoons grated lemon zest
In a small bowl, dissolve yeast in warm water. In a large bowl, combine milk, butter, egg, sugar, salt, yeast mixture and 2 cups flour; beat on medium speed until smooth. Stir in enough remaining flour to form a soft dough (dough will be sticky).
Turn dough onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled, about 1 hour.
For filling, in a small bowl, mix sugar, lemon zest, cinnamon and, if desired, poppy seeds. Punch down dough; roll into an 18x12-in. rectangle. Brush with melted butter to within 1/4 in. of edges; sprinkle with sugar mixture and almonds. Roll up jelly-roll style, starting with a long side; pinch seam to seal. Cut into 12 slices.
Place in a greased 13x9-in. baking pan, cut side down. Cover with a kitchen towel; let rise in a warm place until almost doubled, about 45 minutes.
Preheat oven to 400°. Bake rolls 15 minutes. Meanwhile, for glaze, in a small saucepan, combine sugar and lemonade concentrate. Cook and stir over medium-low heat until sugar is dissolved. Stir in butter and lemon peel; simmer, uncovered, 10-12 minutes or until slightly thickened. Remove rolls from oven; pour glaze over rolls. Bake 5-10 minutes longer or until golden brown. Cool in pan 5 minutes. Run a knife around sides of pan before inverting onto a serving plate. Serve warm.