Hey y'all, hoping I can get some help here!

So I was making a black velvet cake this week with some new black cocoa powder I ordered off Amazon. I made one cake, but when I took it out of the oven, it smelled slightly burnt. I tasted it, and it was more bitter than I was used to and slightly burnt tasting. Thinking I must have left it in too long (I couldn't see if it was burnt because the cake was black already, haha!), I decided to try another recipe. So I whipped up another black velvet cake, and it tasted a little better, but was far too flat and dense. Very frustrated, I decided to try one more recipe. It came out about the same as the first cake, definitely with a stronger flavor than I'm used to and tasting almost a little burnt. At this point, I realized that it must have been the black cocoa powder that was causing the weird flavor.

Here's the black cocoa I was using: link. I've read many good reviews for King Arthur Flour's black cocoa online, so now I'm wondering if the brand that I bought was just not good quality? Does black cocoa give all baked goods a stronger-than-normal, almost burnt-ish flavor? Should I try a different brand, or just combine it with normal cocoa to get a dark black color but more "normal" velvet cake flavor?

I searched through the forum to see if there were any threads like this already but couldn't find anything. If there are, please point me towards them!

I'm open to any suggestions! Thanks in advance!

i've used king arthur and another brand of black cocoa that i have been very pleased with -- you purchased black cacao  -- i looked up the difference between cacao and cocoa and it says the latter is roasted -- the cacao is unroasted and that might be the difference?