The twistor equation states that del _(A')^(A ϕ^(B...E)) = 0, where the parentheses denote symmetrization, in a Lorentz transformation, primed spinors transform under the conjugate of the transformation for unprimed ones, Einstein summation is used throughout, and del denotes the spinor connection, which is equivalent to the Levi-Civita connection on Minkowski space. The zero rest mass equation can be solved by twistor functions. The solution uses ideas from complex variable theory and cohomology.