Plotly figure axes with equal aspect ratio and filling the page

I'm setting up a simple Dash/Plotly app and finding it surprisingly hard to force the figure to appear with desired size and axis scaling.

I simply want my figure axes to have equal scaling on both axes and fill the page appropriately. Right now when I use

yaxis=dict(
    scaleanchor='x',
    scaleratio=1
)

in the fig.update_layout function it puts the axes on the same scale but by shrinking one of the axes, resulting in an unnecessarily small figure.

I want the figure to fill the page appropriately with equal axis scales. How can I do it?