In a Sunday Instagram post, Salma wished Penelope a happy bday and uploaded a series of throwback photos of the actresses smiling and hanging out together at swanky events.

In the caption, Salma thanked God for sending Penelope – whom she described as an angel – to Earth years ago.

Salma also wrote that Penelope has made everyone in her life "crazy, exciting, meaningful inspiring," while also teaching them loyalty and love.

Then Salma heaped praise on Penelope for being an extraordinary mother who has raised two children, Leo, 13, and Luna, 10. Penelope shares the kids with her hubby, actor Javier Bardem.

As you may know ... Salma and Penelope have been close buds ever since Cruz arrived in L.A. for her first American film way back when.

At the time, Penelope didn't know anyone in L.A. and was going to stay in a hotel for the two-month movie shoot.

But, Penelope bumped into Salma who gave her shelter at Hayek's abode, sealing their sisterhood forever. As a side note, the pair have starred in just one flick together – "Bandidas" in 2006.