Creating filesystem from nothing

Creating filesystem from nothing

I need to create filesystem with just one partition from nothing
(/dev/zero). I tried this sequence of commands:
dd if=/dev/zero of=mountedImage.img bs=512 count=131072
fdisk mountedImage.img
n
p
2048
131072
Basically, I need to create 64MB image file filled with zeroes. Then I use
fdisk to create new partition for new filesystem, starting at sector 2048
and using all remaining sectors. But now I'm hitting problems. If I set up
a loop device and format it using mkfs -t vfat, partition table is
overwritten and filesystem is placed to disk. I don't need whole disk
formatted with FAT32, I just need my primary partition to be so.
Does anybody know how can I format only one partition of raw disk image,
not whole image? Please help.