How can I make inner div to 100% width by rotating vertically if outer div is 10% width?

I have two divs (outer & inner). The outer div’s width is 10%. When I put an inner div with 100% width, it contains inside the 10% width of the outer div. That’s exactly how it should behave.

The problem is that I want to rotate the inner div 90 deg and then it should contain the outer div’s height 100%.

Here is the screenshot of the problem.

Here is what I want to achieve

The solution can be in CSS or in Elementor.

Thank you in advance.

When I rotate the inner div 90 deg, it remains the 10% width of the outer div. But it should expand to 100% of the outer div’s height.