In a saucepan, melt butter on low fire.
Add onion, capsicum, pemianto, grated yam and garlic.
Cook for 5 minutes stirring frequently.
Sprinkle about 2 to 3 tablespoon water, cover and let cook till yam is just tender.
Liquidise tomatoes and pass through a sieve.
Add tomato puree and rest of the ingredients to yam mixture.
Cook for further 5 minutes.