Hair dye from black to blonde?

the best thing you could do would be to let the black grow out and let the natural color come through which would then be your healthiest possible hair though< unfortunately that is not possible because you would have major ugly regrowth so I suggest you get the hairdresser to life the color out then your hair will go a brassy orange from being stripped of its color then let your hairdresser put the lightest possible color that she can in it and then get hair treatment to make your hair silky smooth

after all of that which will cost over $100 most likely , you can put blonder foils through it gradually until you can reach your lightest optimum color

I hope this has helped, I know its probably not exactly what you want but I think it might be the only way to do it without cooking your hair and remember once you hair is burnt from straightening, coloring or heat it can never go back to its original state again, thats like saying if you cook chicken you can get it back to its raw state. you cant. by the way dieing your hair black is 90% unsatisfactory in the long run for most people that do it eg. regrowth, hair loss from too much dieing, or wanting to get back to their previous color

GOOD LUCK I SINCERELY HOPE I HELPED !!!