Fill in contour resulting from using vtkCutter (plane) on a vtkFlyingEdges3D generated surface

Using vtkFlyingEdges3D I generated a surface based on a vtkImageData:
Screenshot from 2023-11-14 15-50-37
When applying vtkCutter (with a given plane as the cutting function) I get the contour:
Screenshot from 2023-11-14 15-52-41
Good so far. The problem is that now I would like to infill the region inside of this contour. I decided to apply delaunay2D but unfortunately it did not work due to non-manifod edges. It produce something like this:
Screenshot from 2023-11-14 15-57-01

A few things to consider:

  • I am applying a low pass filter to the output of vtkFlyingEdges3D through vtkWindowedSincPolyDataFilter (with NonManifoldSmoothingOn())
  • vtkFillHolesFilter was tried without sucess (no output)
  • I am only interested in visualizing in 2D. The creation of the 3D surface was done for the purpose of visualizing (in 2D) the intersection of the surface with a given plane.

Can anyone help me with infilling the contour? Might there be another way of doing this with the surface as the starting point?