Here's a simple recipe for home-made tzatziki, it goes very well with off-dry riesling and sherry (and good quality salted crisps)...

1x large cucumber, remove skin, cut in half and remove seeds, grate into a bowl.
Add 1 tbsp of olive oil
Add at least two finely chopped cloves of garlic, more if you like
Add one bunch of spring onion, roughly chopped.
Add greek yogurt, around 400g (? standard pack size, full fat)
Add grated zest and juice of one a lime.
Add a good pinch of chilli powder, more if you like it hot
Season well, especially salt
Stir and leave for at least an hour before eating, it really isnt that interesting if you eat it immediately but is wonderful after three hours or more.

We make this most weekends, this portion will last a couple of days and cost much less than the shop bought stuff, and it tastes better.