Are garlic powder and onion powder considered a Davar charif?
See the contemporary sefer Ohel Yaakov here who discusses a machlokes whether a dry davar charif like black pepper is still a problem for cutting or only a moist one, and he points out that the majority opinion is that even dry spicy things are a problem. In a footnote he remarks that this should apply to onion powder and garlic powder as well.
(By cooking it's even worse, since even dry spices which don't taste so sharp gain their sharpness when they are soaked in a dish. So it could be that even the mekilim would be stringent in a case of cooking if the flavor is very strong. Admittedly by cooking it's rare to use so much that the food is extremely spicy.)
See also the following Q&A, which also explicitly posits like Ohel Yaakov:
[Q] What is the law of onion powder and garlic powder?
[A]Onion and garlic powder fall under the dispute of dry Charif foods regarding whether they are considered sharp. Practically, the final ruling follows that they are considered sharp.
Afterwards I located a sefer called "Davar Charif" which is devoted entirely to the topic of these halachos. Chapter three halacha 1 with footnote 17 discusses the halachos of cooked dishes. While he doesn't mention onion powder or garlic powder explicitly, he does assume that if the entire food tastes extremely spicy (because of added spices, like seasoning to chili) then we give the food the status of being called "davar charif." As far as I can tell, he does not distinguish anywhere between different types of seasonings which cause the spiciness; it's only a question of how spicy (extremely spicy versus mild etc.)
This would seem to differ with the above sources, whereby it's not about if specific ingredients have a status of spicy or not. If you would add so much garlic and onion powder or any spice such that the food became extremely spicy then the food would be a davar charif. It all depends on the level of spiciness.