While the salmon is cooking, whisk together the almond milk and cornstarch. Whisk in the Greek yogurt until smooth. Season lightly with salt and pepper. Pour this into the skillet over and around the salmon. Cook for a few minutes all together, uncovered, until the sauce is slightly thickened. Add the basil and lemon zest at the last minute, just before removing from heat. Adjust seasoning with additional salt and pepper. Serve, drizzled if desired, with the remaining unused olive oil.