There is almost no food which is guaranteed to be safe. If it has nutritional value for a human, it has nutritional value for many microorganisms too, some of which are human pathogens.
So, out of the FATTOM rule, you can already throw out F: you cannot remove the food. A is also not a good candidate - no food is naturally acidic enough, and while there are foods preserved by acidity, an error in processing can lead to the food being dangerous. Also, there are some bacteria and molds which thrive in quite acidic environments (although few of them are pathogens). Oxygen is even worse, as botulinum is anaerobic and very dangerous. Also, once you open the canned food, it can get contaminated again.
Time and temperature are quite good, but they are no guarantee for no food poisoning. First, processing errors are common. Second, you can't sterilize the food in a normal pot, and the remaining bacteria resume multiplying even before it's cooled off enough to eat. And, if it was contaminated before the cooking, the pathogens can have produced temperature stable toxins before you cooked the food.
Moisture is probably the only factor which can produce completely safe food. Most dehydrated food is not 100% safe. Beef jerky, cured hams, dehydrated fruit, nuts and similar can easily grow toxic mold during improper storage. Depending on how much water was removed in the preservation process and where you live, the kitchen shelf can turn out to be "improper storage". Flours are quite safe too, but you have to cook them, and the cooked product is again not guaranteed to be safe.
The only foods which will be completely safe will be the ones which never had any moisture to begin with, and will remain bactericidal if they acquire some moisture from the air. So sugar (either granulated, or hard candy),salt and pure oil can be declared safe from pathogens, but not from some kind of factory mishap where toxins can have contaminated the sugar and oil. A protein powder may fall in this category, I'm not completely sure how little moisture would be sufficient for a mold to grow on it.
And don't forget that you can infect yourself with digestive tract pathogens by handling the food with contaminated utensils or fingers, even if they don't get the chance to build a colony in the food. You could in principle hold your dining room clean to operation room standards, but people get infections in operation rooms too.
Nutrition is off topic for this site, so I won't discuss the wisdom of eating nothing but sugar, oil, salt and boiled water in order to eat guaranteed pathogen free food. For me personally, the trade off is absolutely not worth it.
Best Answer
I don't have a completely definitive answer. However generally, fermentation produces lactic acid which inhibits the growth of harmful bacteria, which is why it is a successful food preservation method. The yeast and bacteria that are responsible for the fermentation are often naturally occurring on many raw foods. For example with lacto-fermented vegetables often all you have to do is submerge them in a salt solution and the naturally occurring yeast and beneficial bacteria will usually just do their thing and begin the fermentation process, which inhibits the growth of bacteria.
This is similar to how sourdough starter works, you simply add water to flour and the naturally occurring yeasts are activated. As the starter ferments, lactic acid is produced, which reduces the pH of the solution, which inhibits the growth of bacteria. This is why you end up with sourdough starter rather than something spoiled. This is also why fermented foods (pickles, sourdough bread, etc) are generally sour in flavor.
Incidentally this same thing is true of wine grapes, if you harvest ripe wine grapes and just leave them somewhere, fermentation will begin because of the naturally occurring yeasts on the fruit, which will eventually produce wine. These yeasts are variable and can be mixed with various bacteria and produce uneven results, so wine makers generally do not roll the dice and add their own preferred yeast instead. But I suspect that this is how wine was made for thousands of years before that technology was developed.
Back to dosa, the dosa batter is usually prepared by combining dal and rice and sometimes salt with water. The dal especially typically has a significant amount of lactic acid bacteria, and the salt, if used, inhibits the growth of harmful bacteria. Many recipes call for fenugreek seeds (not ground fenugreek), which usually contain naturally occurring yeast which helps kick off the fermentation. The rice is usually raw (soaked) before it is ground, and so has not had a chance to sit cooked at room temperature to develop harmful bacteria. The goal of the recipe is to ensure the beneficial fermentation happens instead of the growth of harmful bacteria. The recipe is pretty foolproof which is why dosa have become a dietary staple in such large parts of the world.