1. Cut cucumber into very tiny pieces. if it is a mature one you may remove skin and seeds as they might be bitter. tender ones will be a little sweet.
2. Also finely chop a small piece of ginger and 1 green chilly. grate 1/4 coconut.
3. Mix all the above and add salt to taste.
4. Now prepare a tadka / tempering with oil, mustard, curry leaves, urad dal, hing and one red chilly.
5. Add the tadka and mix well. preferably prepare this just before serving else cucumber will release water.