Dal is lentils, water, salt and a tempering. Four things. Which is precisely why it's difficult — there's nowhere to hide and the technique carries everything.

Here are the things that most commonly go wrong.

The lentils aren't cooked enough

The single most common issue. Properly cooked dal has lentils that have collapsed — the individual pieces have broken down and thickened the liquid.

Lentils that hold their shape are undercooked, whatever the packet time says. The texture should be creamy, not soupy with objects in it.

Cooking time varies enormously with the age of the lentils. Older stock takes considerably longer and sometimes never softens fully, which is worth knowing if a batch is stubborn — it may not be your technique.

Hard water also slows softening. If your lentils never cook properly and you're in a hard water area, that's a plausible cause and a pinch of baking soda helps, used sparingly since too much affects flavour and texture.

Salt timing

Contested and worth understanding rather than following a rule.

The traditional advice is to salt after cooking, on the reasoning that salt slows softening. The effect is real for some pulses, particularly whole ones with skins.

For split lentils it's a smaller effect and salting during cooking seasons them from within, which produces a better-tasting result than salting at the end.

The compromise most cooks arrive at: a small amount during cooking, adjusted at the end. If your dal tastes flat despite adequate salt, this is frequently why — salt added only at the end sits on the surface rather than through it.

Not enough fat

Home dal is frequently made with a fraction of the fat used traditionally, and it shows.

Fat carries the aromatic compounds from the tempering, provides mouthfeel, and rounds the acidity. Dal made with a teaspoon of oil tastes thin because it literally is.

You don't need an alarming amount. A tablespoon of ghee or oil for four servings is not excessive and transforms the result.

One tempering instead of two

The technique that most separates restaurant dal from home dal.

Many traditional preparations use a base tempering — onions, ginger, garlic, ground spices — cooked properly and combined with the lentils, followed by a finishing tempering of whole spices in fat poured over at serving.

The first builds depth. The second adds a fresh aromatic top layer. One without the other gives you either depth without brightness or brightness without body.

If you make one change to your dal, this is the one.

The onion isn't cooked

Where the base tempering includes onions, they need considerably longer than most recipes suggest.

Onions go through stages: translucent, then golden, then properly browned. Each stage tastes different and the sweetness that gives a dish depth only develops in the later ones.

Recipes saying five minutes are describing translucent. Properly browned onions take fifteen to twenty-five minutes over medium heat, stirred occasionally, with a pinch of salt to draw out moisture.

Rushing this over high heat gives you burnt edges and raw centres, which tastes acrid rather than sweet.

No acid

Dal without something sour is flat, and this is frequently the missing element when everything else has been done correctly.

Depending on the region and the dish: tamarind, lemon or lime juice, tomato, amchur, or yoghurt.

The acid should go in at the right point. Tamarind and tomato early enough to cook. Lemon at the very end, because heat destroys its aroma. Adding lemon to a simmering pot wastes it.

Under-seasoned generally

Lentils absorb a lot of salt and dal needs more than seems reasonable. Taste and adjust at the end, and expect to add more than you think.

The test: if it tastes almost right but slightly dull, it usually needs salt rather than more spice. Adding more spice to an under-salted dish makes it muddy.

Whole versus split

Worth knowing because they behave differently and aren't substitutable without adjustment.

Split lentils without skins cook fastest and break down readily into a creamy texture.

Split lentils with skins hold more texture.

Whole pulses take substantially longer, generally benefit from soaking, and produce a completely different result — heartier, with distinct texture.

Recipes are written for specific types and swapping without adjusting time and liquid produces disappointment that isn't your fault.

The finishing touches

Small things that make a noticeable difference.

Fresh coriander added at the very end, not cooked.

A knob of ghee stirred in just before serving, separate from the tempering.

Resting for ten minutes off the heat before serving, which lets everything settle and the flavours combine.

And dal thickens as it stands, so it should look slightly loose when you take it off. Adjusting the consistency at the moment of serving rather than earlier avoids the thick paste that a well-made dal turns into after twenty minutes in a pot.