Preheat oven to 325. Place butter on 15 1/2 x 10 1/2 jelly roll pan; place in oven to melt butter, about 7 minutes. Meanwhile, beat egg whites with salt until frothy; gradually add sugar, beating to stiff peaks. Gently fold in almonds and cinnamon. Pour almond mixture onto jelly roll pan; toss with butter. Bake about 40 minutes, tossing every 10 minutes, until almonds are crisp. Serve warm or at room temperature. Store cooled almonds in airtight container up to 2 weeks.