Specifically in this recipe: Tiramisu-II  The reason why I'm asking this is I only have vodka at home, and I rarely drink. So I don't want to buy any kind of liquor just for three tablespoons of it. Plus, alcohol is very expensive where I live. 
What I ended up doing was using 1/2 tsp of almond aroma and 1 tbsp of vodka. The taste was good, but I could have put much more vodka. I'll do that next time. 