In our house, uttapam is a by-product of dosa :). It's when there is left-over batter from making dosas that we utilize it to make uttapams. That's how we got hooked to uttapams and realized what experts we were at it! Uttapam is easier to make as compared to dosa because it doesn't require the spreading-skills. So the recipe I describe out here also started with the making of dosa.
For the base
Salt to taste
For the toppings (qty varies on your liking)
Onion (finely chopped)
chillies (finely chopped)
coriander (finely chopped)
tomatoes (finely chopped)
1. Prepare the batter
Take the rice flour and urad flour in the ratio of 2:1 by volume. So if you take 1 cup of urad flour, you need to take 2 cups of rice flour. Yes, we use flours instead of grinding rice/urad dal. It's the easy way out and makes no difference! Ok, now let's add some water to the mixture. Add enough water to make a batter. Add salt to taste. Hmm...now how to decide the consistency. Be on the conservative side because we can add water later after the batter has fermented. Once the batter is made, keep it for a night (or two) to ferment. Duration depends on the weather at that time. If it's warm then it would only need a night. If you don't know how to identify a fermented batter, note the texture of the batter when you set it to ferment. The next day if you see that the texture has changed then it means that fermentation has started. If the level of the batter has almost doubled, then the batter is definitely ready!
We now have the fermented batter. Let's do a consistency check. Take a serving spoonful of batter and drop it from a foot's height, it flows in one single strand then you're ready. Wait - we need to make sure it's not too thin. For that you can cross-check with the video here.
2. Pre-heat the griddle to a medium-high temperature then once you're ready reduce it to medium heat. I prefer non-stick griddles as it's easy to make and requires less oil.
3. Take a big serving spoonful of the batter and drop it on the griddle. Spread it a little to the size you want. Don't make it thin like dosa, it should be thick. Now spread the topping all over it. Spray/sprinkle some oil on the circumference of the uttapam and over it. If you're using non-stick then you need really small amounts. Let it cook on the bottom side, once done flip it to cook the other side.
Wasn't that easy?