As if Berkshire Hathaway's (BRK.A 0.64%) (BRK.B 0.54%) huge position in Apple (AAPL -0.57%) wasn't already enough of an indicator of famed investor Warren Buffett's confidence in the stock, Buffett told CNBC this week there is a better way to judge how much Berkshire likes its stock holdings: the rate at which his company is buying shares.

Based on this measure, Buffett absolutely loves Apple stock -- because Berkshire's been buying Apple shares in droves.

A packed Apple store after the iPhone X launch

An Apple store. Image source: Apple.

How to tell what stocks Buffett likes

After Berkshire increased its position in Apple stock during its fourth quarter by 31.2 million shares, or 23%, Apple became Berkshire's largest holding when measured in dollars. When including Berkshire's 325.4 million shares of Kraft Heinz -- which Berkshire excludes from its list of common stock investments on its financial statements since Berkshire is a part of a control group and is required to account for this investment using an equity method --  Berkshire's common stock investment positions behind Apple when ranked by dollar value are Wells Fargo (worth $27.6 billion), Kraft Heinz (worth $22.6 billion), and Bank of America (worth $22 billion).

So, just by ranking Berkshire's investments by dollar value, it's clear that Berkshire likes Apple stock. But Buffett implied to CNBC that viewing his stocks this way may understate how optimistic he is about investments Berkshire has been actively purchasing.

"If you look at our holdings, you would assume that we like them in the order in which they rank by dollar value of holdings," Buffett told CNBC, "but if you look at them in terms of recent purchases over the last year we've bought more Apple than anything else."

Berkshire started buying Apple stock in early 2016, but ramped up its purchases of the tech giant toward the end of 2016 and in the beginning of 2017. Notably, Berkshire's purchase of 31.2 million Apple shares in the fourth quarter of 2016 represented a reacceleration in Berkshire's purchasing of the stock. In the third quarter of 2017, Berkshire added just 3.9 million Apple shares.

But why does Buffett love Apple stock?

Later during the interview, Buffett explained a bit of the thesis behind his confidence in Apple stock, calling the company "an extraordinary consumer franchise."

"I see how strong that ecosystem is, to an extraordinary degree," Buffett said "... You are very, very, very locked in, at least psychologically and mentally, to the product you are using."

To this end, Apple has recently demonstrated the strength of its ecosystem by recording record iPhone revenue during its holiday quarter as consumers gobbled up iPhone units even as the company launched them at their highest prices ever.

Apple's strong consumer franchise has also been exemplified in the company's recent ability to consistently post rapid growth in its services and other products segments, which include revenue from products and services that complement the overall Apple ecosystem of hardware, software, and services. These two segments saw revenue rise 23% and 33% year over year, respectively, in the trailing-12-month reported periods. This growth highlights how Apple customers are buying up newer products like the Apple Watch and AirPods9, and spending more money on the Apple Store and services like Apple Music.

iPhone X, Apple Watch, and AirPods charging on Apple's AirPower mat

Apple products. Image source: Apple.

It's easy to make a case for Apple's overall attractiveness as a stock when looking at the company's underlying fundamentals. In the trailing 12 months, revenue and earnings per share are up 10% and 22%, respectively. Further, Apple expects robust growth to continue, with management guiding for year-over-year revenue growth of about 13% to 17% year over year in its second quarter of fiscal 2018. Notably, the midpoint of this guidance range would mark an acceleration in Apple's recent year-over-year revenue growth.

Even with Apple's strong underlying business and its powerful consumer franchise, the stock trades at just 18.5 times earnings.

No wonder Buffett loves Apple stock.