Concatenate multiple files but include filename as section headers

I would like to concatenate a number of text files into one large file in terminal. I know I can do this using the cat command. However, I would like the filename of each file to precede the “data dump” for that file. Anyone know how to do this?

what I currently have:

file1.txt = bluemoongoodbeer

file2.txt = awesomepossum

file3.txt = hownowbrowncow

cat file1.txt file2.txt file3.txt

desired output:

file1

bluemoongoodbeer

file2

awesomepossum

file3

hownowbrowncow