The 32-year-old hit back from throwing away the BMW PGA Championship by capturing the Madrid Masters a week later.
Donald was joint leader with Simon Khan at Wentworth when he took a double-bogey seven on the penultimate hole, but then an eagle at the 16th hole of his final round in the Spanish capital helped him to end four years without a victory.
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Hide AdHe said: "Obviously it's been a great month from a personal point of view and to put Wentworth behind me with a win in Madrid seven days later gave me a good boost of confidence.
"Obviously I am happy about being the Golfer of the Month as I don't think I've received one of these since I won back-to-back in 2004."