Mobile phone photos - even if it does come from the latest model - will not give you the picture quality or depth-of-field required to render the kind of photo one might expect to see on a recipe book. Given that you're designing your own covers, I doubt you have the budget to hire a professional, so you likely don't have much choice but to pursue stock imagery - however disingenuous that might be, in the end. Rather, you've got to make sure that the cover is beautiful enough to make up for the deficiencies in imagery.
Doing a quick search of self-published cookbooks, there are a few out there, and many of them look pretty awful. I found an interview with one self-publisher who has a half-decent cover and this is what she said about part of the process: "My friend Signe Birck, an incredible food photographer, agreed to take the photos, so I decided that we should just go for it! We didn’t have the budget to rent out a studio space or hire a styling team, so we just worked as a duo (with the help of my incredible intern Elise Inman), shooting in my apartment once or twice a week over the course of five months... I hired Katie as designer and Lauren Salkeld as editor."
It's also worth pointing out that she was a professional: "By this time, I had gone to culinary school, cooked professionally for 10 years, and written for major food magazines and websites."
Reading her account is exactly how I would expect someone who is serious about publishing cookbooks to go. They were fortunate enough to have a photographer friend - who one assumes did the work for free - and she hired the relevant professionals to fill the gaps in their own skillset (editing and designing). She also documented the process of making the cookbook on a blog before publishing, which would have served as great marketing leading up to release.
Here's her cover next to yours. You can see the difference; it's night and day. A lot of self-publishers design their own covers and I see hundreds of them on this forum and I am yet to see one (one!) that is even remotely professional looking. I don't say this to disparage the community, only to point out that to get from where you are to an even remotely professional look without the use of a designer is a long, up-hill struggle.
I often get questions posed to me about branding, about how to design a logo for free or where to get cheap work and my answer is always the same: "you get what you pay for" and if you really cared about what you're doing you would make sure you're getting the very best possible.
So, a little late to the game, my question is: do you really care about these books or are they just throwaway projects to end up lost on Amazon like most self-published books, or is it something you're passionate about and really want to create something meaningful? If it's the latter, you may need to change your tactics drastically.
Here is the link to the interview I mentioned.