If your oil starts getting too hot, reduce the heat. Use a food thermometer to make sure the oil stays at 350 Fahrenheit (175 celsius).
If you see your buñuelos getting cracked, remove them from the oil ASAP, this is a sign that the oil is too hot or the dough needs to be kneaded for a smoother consistency.
The oil you use for buñuelos should be new oil, not one that you have previously fried something else in. I used canola oil.
I bought my cheese already grated finely. If grating your own cheese make sure it is very fine to achieve a smooth dough