Investing your hard-earned money into stocks that can provide you with attractive passive income is one of the best ways to grow your savings toward your goal of retirement or financial freedom.

Furthermore, when you buy stocks that pay you monthly rather than quarterly, you can put that money back to work much quicker, taking advantage of the incredible power of compound interest.

The key for investors, though, when buying dividend stocks is to ensure you're finding affordable stocks to buy but also reliable ones.

You certainly don't want to overpay for your investments, but you also don't want to find super-cheap, low-quality stocks offering sky-high yields, which could be at risk of being cut their dividends in the near term.

So, if you're looking to add high-quality stocks that generate significant passive income to your portfolio, here are two of the best today, each trading at attractive valuations.

One of the best Canadian stocks that passive-income seekers can buy today

There's no question that one of the best passive-income-generating stocks on the TSX today is Freehold Royalties (TSX:FRU).

Freehold is an energy stock that consistently acquires land in energy-rich areas that other energy companies can use to produce oil and gas in exchange for a royalty.

It's a lower-risk business in the energy sector that doesn't require Freehold to spend essentially any capital expenditures at all, unlike its producer peers, allowing it to constantly generate millions in cash flow, the majority of which it pays back to investors through a dividend.

This business model allows Freehold to pay a significant dividend—currently yielding 7.95%—while still retaining cash it can use to expand its future operations, such as acquiring more land.

Freehold aims to keep its payout ratio at roughly 60% of its free cash flow, ensuring that the dividend is sustainable and allowing Freehold to build a significant cash position for those future acquisitions it has its sights on.

Plus, because the passive-income stock owns land in Canada and the U.S., its diversification helps mitigate risk and expose Freehold to more potential growth.

For example, in the second quarter, the amount of oil produced on its land in Canada was flat quarter over quarter. However, in the U.S., the amount of oil produced on Freehold's land increased by 9% quarter over quarter.

Therefore, given its lower-risk business model, diversification, sustainable dividend, and the fact that Freehold trades toward the bottom of its 52-week range, it's certainly one of the best stocks that passive-income investors can buy now.

A reliable dividend stock offering a yield of 7.2%

In addition to Freehold, another high-quality royalty stock that's ideal for passive-income seekers and returns cash monthly is Pizza Pizza Royalty (TSX:PZA).

Pizza Pizza is a high-quality dividend stock to buy now due to its significant yield and the fact that its revenue and net income hardly fluctuate year over year.

Since the stock earns a royalty on all the sales made at Pizza Pizza and Pizza 73 locations across the country, it's mainly focused on growing or at least maintaining the aggregate sales made across the country.

Therefore, Pizza Pizza's revenue is typically stable quarter over quarter and year over year, making it an excellent stock for passive-income investors to buy and hold for the long haul.

Another benefit of Pizza Pizza, especially in this economic environment, is its status as a well-known, convenient, and low-cost option.

While many discretionary stocks are at increased risk during economic uncertainty, Pizza Pizza's operations are far more resistant due to its wide variety of menu options and prices that are typically in line with or cheaper than those of other restaurant businesses.

Therefore, while analysts do expect a minor pullback in sales this year due to the economic climate, the current estimate is for sales to decline by just 0.4% this year before rebounding next year and growing more than 3.5%. It's also worth noting that its normalized earnings per share are expected to fall by less than 1% as well, which shouldn't have any impact on the dividend.

Therefore, if you're a passive-income seeker looking to add high-quality dividend stocks to your portfolio today, Pizza Pizza and its attractive monthly dividend is undoubtedly one of the top TSX stocks to consider.