The ends of my hair are a bit lighter than the rest of my hair...what do I do?

1 1/2 years ago I dyed my hair a darker espresso brunette with Feria. Big mistake! My natural hair color is medium to dark auburn/brunette. But the Feria, rather than permanently dying my hair a darker brunette, actually turned my hair into a fried, brown mud color...and after two days, the dye rinsed out, leaving my hair ruined and a light brown gold color (lighter than my natural color). I guess the Feria must have first "lifted" my natural brunette color to a lighter level before depositing the ugly mud color onto my strands. Well, a couple years later, I have gotten scheduled trims, but there is still this line of demarcation that shows lighter ends and darker roots. I don't want to dye my hair ever again, plus, I want to grow my hair to waist length. What do I do to get a more uniform color all over without dying or using henna? The color change at the ends is probably one or two levels lighter than the rest of my hair. I have baby fine hair in the front and medium thick in back.