Greek Yogurt with Lemon Juice (Best Option)
1/4 cup Greek yogurt + 1 tsp lemon juice per 1/4 cup buttermilkGreek yogurt offers a thick, creamy base similar to buttermilk, while lemon juice adds the necessary acidity to replicate buttermilk's tang. This combination helps maintain the balance between the sweet mascarpone and coffee flavors.
For best results, mix the lemon juice into the Greek yogurt and let it sit for 5 minutes before using to allow the acid to slightly curdle the yogurt, mimicking buttermilk's consistency. Avoid using overly thick Greek yogurt to prevent heaviness.
Compared to buttermilk, this substitute preserves the dessert’s lightness and tang without introducing off-flavors, making it the closest match in tiramisu recipes.