@angeloaliano1
To customize both aspect ratio and plot aesthetics you can use PlotlyJS.jl:
using PlotlyJS
include("plotlyju.jl"); # style file: https://gist.github.com/empet/6b4f441ed96d724d67ff77f1fb8b0a79
f(x,y) = y < x ? cos(8x) + sin(8y) : NaN
xg = -2:0.02:2
z = [f.(x,y) for x in xg, y in xg];
trace = PlotlyJS.surface(x=xg, y =xg, z=z,
colorbar_len=0.7)
pl = PlotlyJS.plot(trace,
Layout(width=600, height=600,
scene_aspectratio=attr(x=1, y=1, z=0.5)),
style=plotlyju)