Maximization of the ratio between Kitaev and residual Heisenberg interactions is a major goal in the current research on Kitaev-Heisenberg magnets. Here we investigate Kitaev-Heisenberg exchange in a recently discovered crystalline phase of α-RuCl3 under pressure - it displays unusually high symmetry, with only one type of Ru-Ru links and uniform Ru-Cl-Ru bond angles of ≈93∘. Using quantum chemical calculations, we find a very small nearest-neighbor Heisenberg J, which yields a K/J ratio between Kitaev and Heisenberg exchange as large as ∼100. We also find that this is associated with vanishingly small d-shell trigonal splittings, i.e., minimal departure from ideal jeff=1/2 moments. This reconfirms RuCl3 as a most promising platform for materializing the much sought-after Kitaev spin-liquid phase and should stimulate further experiments under strain and pressure.