Add lemon juice in milk and keep aside for 5 minutes.
Add the mixture in the jar with the cream.
Cover the jar and keep aside for 24 hours at room temperature.
Refrigerate the jar for 6-8 hours.
It is ready to be used now.
Use low-fat cream to make it. The fat content of the cream should be 18-20 %.You can also make buttermilk using vinegar. Just replace lemon juice with vinegar and follow the rest of the steps as listed.Another way to make it is by using yogurt as the fermenting agent. Just add a tsp of plain live yogurt per 1 cup of cream and leave on the counter for 6-8 hours. Then refrigerate for another few hours.