Plot three dataframe columns as x, y and value as contour

Question

I want to plot preferably a contour plot from three columns of a dataframe df:

import pandas as pd

ids =[1, 2, 3, 1, 2, 3]
lons = [3, 5, 6, 3, 7, 8]
lats = [10, 10, 10, 30, 30, 30]
ratio = [.1, .4, .2, .3, .4, .5,]

df = pd.DataFrame({'ids' : ids, 'lons' : lons, 'lats' : lats, 'ratio' : ratio})

How do I create a plot that uses lons on the x axis, lats on the y axis and then creates a contour plot as the example below with the corresponding values ratio on that location?

What I ultimately want, something like this:

I realize the function wants a 2D grid as input, but how would I do this considering the values are stored in a single column as well?