That is number 40 for Alonso and it wasn't cheap. His blasts rarely are.
With that, he breaks the NL rookie record for home runs. Frank Robinson long held that record with 38, but Cody Bellinger hit 39 in 2017 to take the lead and now Alonso has stolen that one. The rookie record for either league is 52, which was set by Aaron Judge in 2017. Alonso has a real shot at that one. In fact, his current pace (40 homers in 124 Mets' games) is 52.26, so it appears it'll be close.
Next up on the list for Alonso, though, is the Mets' franchise record. It's 41 (Todd Hundley and Carlos Beltran and).
Also of note here is that, unfortunately, Fernando Tatis Jr. is likely out for the season ( ). This matters because Tatis was Alonso's chief competition for the NL Rookie of the Year. With Tatis having only played 84 games and Alonso smashing home run records, it would appear this thing is in the bag now. I'm sure some would mount an argument for Bryan Reynolds, who entered Sunday hitting .329, but Alonso's case is far more complete.
As Alonso told me earlier this season, he feels like he's living a dream. His dream now includes the NL rookie home run record and will soon have the Mets franchise record, possibly the MLB rookie record and likely the NL Rookie of the Year. Not too shabby, as far as dreams go.