Many reporting tools use algorithms that can't easily factor Cloudflare into the time to first byte calculation.

Please see this comment from describing how Cloudflare would still make your site faster,

even if it appears that the first byte numbers appear to be high. We also have written a fairly extensive blog

post about Cloudflare and Time to First Byte that explains more about First Byte times and Cloudflare &

why the Time to First Byte metric is really not the most important measure of how fast your content is loading.