Prepare the tomatoes by blanching them. Wash the tomatoes and add them to a saucepan with boiling water. After 30-40 seconds, place the tomatoes in a bowl with ice-cold water. In 1-2 minutes, you will see the skin coming off the tomatoes. Peel the skin off.
To a food processor, add the tomatoes, onions, and chilli. Pulse, but not too heavily. The tomatoes and onions must still retain texture.
Pour this tomato-onion-chilli mixture to a large bowl. Add the lime juice, salt and pepper, and toss well to combine.
Add the mango pieces. Stir well, cover, and let it sit for up to two hours in the refrigerator before serving.
Serve the Moyo sauce spooned over grilled fish or roasted or pan-seared meat.