Here are three stocks with buy rank and strong momentum characteristics for investors to consider today, May 21st: Onto Innovation Inc. (ONTO) : This manufacturer of process control tools for optical metrology has a Zacks Rank #1 and witnessed the Zacks Consensus Estimate for its current year earnings increasing 6.6% over the last 60 days. Onto’s shares gained 27.8% over the last three months compared with the S&P 500’s advance of 4.8%. The company possesses a Momentum Score of A. Southern Copper Corporatio ...