Orange Butter

I've made apple-butter before, so I was intrigued when I came across this recipe for Orange Butter. It was delicious on breakfast crepes. I'll try it tomorrow morning on toast. It's also a less-sweet option for an ice cream topping, or drizzled over a bowl of fresh fruit...

Ingredients: 
½ C butter 
½ C sugar
½ C fresh orange juice
1 tsp orange zest
½ lemon, juiced
1 tsp Grand Marnier (or other orange-flavored liqueur)

Directions:
Combine sugar, butter, juices and zest in saucepan and cook for 10 minutes until caramelized to a rich, golden color. Remove from heat, and liqueur; return to heat and whisk until reduced and syrupy -- about another 10 minutes. Remove from heat; cool. Serve slightly warm.